I use Ad-block Plus with Firefox.
If you were using I/E did you download another host file to use.
I found that with I/E it was the new Host file that was slowing it down.
So I removed it and it is much quicker at opening new web pages now.
Another one to try is command prompt and type in ipconfig /flushdns then press enter on the keyboard.
It should tell you the DNS Cache has been flushed if so reboot and see if it works any quicker.