Problem with Web Browser or possibly internet

When i first turn on my computer, the internet seems fine.

It works just fine until some point, when i try to use it again, it takes forever to load, or sometime just doesnt.

I use firefox and the bottom says
“Waiting for ……”
The right hand side shows the bar go half way through and it seems to stay there.

I dont understand what the problem is as i use trillian, but it works just fine.

I changed browser to chrome, IE, etc, and they all dont work for some reason.

Also some certain websites that i used to open cannot be opened even when it works fine.