There are a ton of possibilities. Among others..
Page downloads can choke for the same reasons that downloads can choke -- high traffic on the server.
The Web server or host may be having problems running its own scripts for one reason or another.
You might have a problem with your virtual java machine (assuming Windows here). Installing / re-installing latest version might help.
Your browser might not be compatible with the markup language or client scripts the Web sites you visit are asking it to run. This might be either your browser's fault or the Web site's fault. (After all, there are people who are writing some pretty crappy markup language and bad scripts out there -- even on very big-time sites.)
You might be experience big hold-ups in load time because of things like ad banners and other crud that could be loading from remote domains that are linked from the pages you are visiting. These can be particularly annoying.
Those are just a few off the top of my head.
...
You can try to find out whether the problem is intrinsic to your system by visiting the same pages at the same time with another system. If both are slow, then the problem may be at the other end. (Though, of course, it's possible that both systems you're using are fouled up in some way.) Or, if the same page chokes at a high traffic time of day but flies onto your screen at 2 AM, then it's a foregone conclusion that the problem is at the other end (or somewhere between your end and the other end).
If you want to post back with really precise observations about browser behavior and which sites you're having trouble accessing someone might be able to help you narrow down the list of suspects. I hope you'll find a way to get an improvement in the behavior.
Regards,
Jim
Facebook
Twitter