Slight problem, can someone help please?

Right, I apologise in advance for my lack of knowledge and poor explanation as to what's going on... Ok, I'm on my laptop as normal, I haven't touched any settings lately but something has changed, any site that I normally frequent looks different, for example I post on another forum and the site looks stupid now, you have to scroll down for posts when you didn't have to, I can't use the quote or smiley functions on the site either for no apparent reason, another form and the site is different colour than it normally is just loks weird, then even on something lie Facebook when I click someones page it doesn't look right. I mean, I can still do what I need to do it's more an annoyance than anything but I cant see what has changed either. I use Firefox, so I uninstalled and re in stalled, that's about all I have done, I looked at settings like add-ons and all this messing, but I am clueless, any ideas anyone, I know it's a bit vague but any help is appreciated.