Firefox 31 keeps asking for Proxy Authentication

The tor guys should have plenty of information with setting up SOCKS proxy authentication: just looking through the settings for Firefox, preferences->advanced->network->Connection Settings->Manual proxy configuration has a SOCKS (v4 or v5) host setting that should get you on your way, although I'm not sure if it also does authentication. Some sources say it does, some say it doesn't (in the form of a pop up on connection asking for credentials).

If the vanilla settings don't do the job, foxyproxy might do it (at least as of 2007, at http://davidtse916.wordpress.com/2007/07/26/switch-proxy-settings-on-firefox-using-foxyproxy/). Note: this is for 3.0.14, so it may be a bit different for 3.5.

I too experience this with a server hosted within our University. It appears to be the way that Office handels the requesting of a Office file from the web. Servers which don't offer WebDAV or other ability for users to save files on the server should have some verb/extensions disabled as outlined.

Microsoft’s Knowledge Base article 2019105 offers the best insight into why this occurs, and the suggested options for addressing it. KB article: http://support.microsoft.com/kb/2019105

Cause:

When Internet Explorer opens an Office document, the appropriate Office application is started with the path of the document. The Office application then tries to access the document directly from the server. This differs from other browsers and other file types. Most browsers download the file and call the application to open the file from the local cache. However, when this occurs, if the opened file is changed and saved, the changes are only made to the local copy and not to the server copy.

To establish the richest experience possible, the first thing that the Office application does is communicate with the server to determine the server type and what web authoring protocol is available. The application does this by making an OPTIONS request directly to the server.

As a new process accessing the server, the Office application is required to renegotiate authentication. This method is more secure than a method in which the new process uses an existing authentication that was established by the browser.

The article’s recommendation is that when users will not be attempting to save files back to the server directly addressing this should be completed on the server side. Specifically disabling the support of OPTIONS and PROPFIND verb/extensions.