I had a lot of problems with my system and had to reinstall it. One of them was these very messages. After reinstalling the system and using the same icons, I get the warnings again and am wary of future problems. How risky is this and should I remove the icons-theme?
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:553:10: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:553:12: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:553:14: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:553:16: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:574:10: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:584:11: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:588:16: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:589:17: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:601:13: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:602:16: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:648:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:649:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:661:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:692:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:694:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:746:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:747:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:794:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:795:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:943:15: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:945:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:967:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:968:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1032:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1032:23: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1045:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1177:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1222:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1223:14: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1223:16: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1223:18: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1223:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1229:24: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1229:26: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1230:21: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1230:23: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1230:25: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1239:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1239:23: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1239:25: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1240:14: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1264:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1264:26: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1270:22: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1270:24: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gtk-widgets.css:1271:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gnome-panel.css:8:10: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gnome-panel.css:23:20: '' is not a valid color name
(gedit:637): Gtk-WARNING **: Theme parsing error: gnome-terminal.css:23:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: gnome-terminal.css:56:1: Expected a valid selector
(gedit:637): Gtk-WARNING **: Theme parsing error: unity.css:11:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: unity.css:21:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: unity.css:21:21: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: unity.css:21:25: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: nautilus.css:11:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: nautilus.css:32:16: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: nautilus.css:64:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: nautilus.css:64:22: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: nautilus.css:65:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:5:14: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:10:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:33:10: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:33:12: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:61:23: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:127:22: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:161:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:163:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-dark.css:178:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:5:14: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:10:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:33:10: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:33:12: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:66:23: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:132:22: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:166:20: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:168:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:183:19: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:207:15: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:207:17: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme parsing error: menus-darker.css:207:21: Not using units is deprecated. Assuming 'px'.
(gedit:637): Gtk-WARNING **: Theme directory actions/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory animations/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory apps/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory categories/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory devices/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory emblems/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory mimetypes/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory places/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory status/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory stock/16 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory actions/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory animations/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory apps/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory categories/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory devices/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory emblems/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory mimetypes/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory places/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory status/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory stock/22 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory animations/24 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory apps/24 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory categories/24 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory devices/24 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory emblems/24 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory mimetypes/24 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory places/24 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory stock/24 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory actions/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory animations/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory apps/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory categories/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory devices/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory emblems/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory mimetypes/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory places/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory status/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory stock/32 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory actions/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory animations/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory apps/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory categories/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory devices/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory emblems/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory mimetypes/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory places/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory status/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory stock/48 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory actions/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory animations/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory apps/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory categories/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory devices/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory emblems/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory mimetypes/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory places/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory status/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory stock/64 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory actions/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory animations/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory apps/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory categories/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory devices/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory emblems/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory mimetypes/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory places/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory status/96 of theme malys-uniblue has no size field
(gedit:637): Gtk-WARNING **: Theme directory stock/96 of theme malys-uniblue has no size field
Best Answer
This error indicates that the software is using valid GTK library calls with a newer version of the GTK library. Sometimes during software development it is desirable to get rid of the, "old way", to do things while maintaining backwards compatibility. This is accomplished by marking the undesired calls deprecated. This tells the developer that their code is valid in this release, but in the future their code will need to be updated to work with a new version of the library, possibly many releases down the road.
In this case, GTK wants to be more strict about including units on dimensions. It tells the developer that GTK is assuming the units are pixels, which is the exact assumption that the software developer made in the first place.
That is a long and very complicated way of saying that these warnings are for the developers of the icon-theme, and do not reflect actual run-time problems.
Using the Ubuntu software repositories, you will not be given incompatible programs and libraries.