Well it could be popular so it slows downs but not only that if it has got lots of graphics which tkes up a lot of memory tht mkes it slow down so i have got a top tip for you (google chrome members only):
Below the x at the top of the screen to close down the webpage there should be three lines click on that then go donw to history then click on that the history should come up.Now clear your history!
Now your websites should be a lot faster!
(Sorry if this doen't work for you but it worked for me yesterday)
If you would like to chat or ask questions feel free to send me a message and I'll get back to you as soon as possible