icloudsafari
I'm using 10.10.3. iCloud keychain is enabled.
Anyway, I find that Safari will ask to save passwords for some sites but not for others.
examples of sites where I get prompted: eBay, amazon, some local discussion forum, stackexchange
examples of sites where I don't get prompted: macrumors, xdc-developers and many others
I've checked the settings and "Auto-fill username and passwords" is enabled i the password tab. I've removed all passwords but it's still happening.
Any ideas on how to fix it?
Yes. Go to the Settings app, and select safari. There will be a section called "Autofill", and you can enable it to save your passwords and auto-fill your personal information taken from the address book. Also, iOS automatically saves all Wi-Fi passwords, so there is no need to save it manually yourself.
Make sure you don't have autocomplete=off in any of the forms. This is the primary way that a website can tell a browser not to save passwords. By default, if the website doesn't have anything, the browser will be happy to save passwords, so odds are that your website contains something like that somewhere.
Best Answer
This is, technically, not an answer but might be a reason why some sites do not save passwords.
They (those web sites/pages) have code in them to tell the browser to not save the password.
I used to have a JavaScript bookmarklet that would (with varying levels of success) remove the code that said "don't save the passwords" but when I moved over to 1Password I stopped needing that.
Possibly a password manager might do that for you (there are free ones, I believe) or a bit of google-fu might find you that bit of JavaScript that worked some of the time in telling sites to stop telling your browser to not save the password.