For the last four days I have not been able to hide certain news feeds like I used to do.
Nor can I post any pictures anymore, these features just are not working when you click on them anymore. What could be causing this?
Try out this on different browser, sometimes it could be a browser issue
Try with a diiferent browser say Chrome
I'm going to go ahead and echo what other people said: try another browser (I recommend Chrome) and see if that helps, or clean out Firefox with CCleaner. Don't mess with registry cleaners, though: they're far more likely to break things than help, in my experience, and I don't think the registry is the problem in your case anyways.
Start Firefox in 'Safe' mode (without any extra's loaded) and try again. This will eliminate the possibility of a rouge or bad addon.
Have you tried with another browser? if it works the clean windows and firefox with ccleaner, wise registry cleanner...