I'm not sure what the problem is here. For some reason in the last couple of days more specifically I've noticed my Macbook Pro lagging on Firefox, especially videos on YouTube, and webpages (text will lag when typing etc) I'm not entirely sure whether this is just related to Firefox for the simple reason that if I load an App it takes a small amount of time to think before loading up. I don't know if this is normal when you have used your laptop for some time or installed stuff on it. I cleared out the cache in any case, and cookies etc. Checking Activity Monitor everything *looks* peachy, but I'm not sure what to look for. In any case only 3% roughly of CPU usage is used so it can't be that. Safari is a lot smoother, videos seem to run better, and it doesn't lag *as* much. Is this a firefox thing or is it possible it could be my Macbook? I recently only got my Macbook Pro about three months ago. It's the 2012 model. I have 400GB of HD space remaining so no problems there. I have 4GB of RAM. Running Mavericks atm.