Blank web pages

Hi,

anybody know why would I get a blank pages in all my 3 browsers( Safari, FireF. and Opera) for certain websites that I use to access with no problems? There is a website where I have a membership and need to login.
Also quiet often if I click on some of the google results I'm being taken god knows where (mainly to Yellow Pages or some other kinda keyword related pages)

I do not have any firewall or virus protection software running. My machine is less then 4 months old. I switched Internet provider and still have the same problem. Sometimes as a fluke on the other network or whatever one of my browsers will connect to a site after I enter my login it gives me another blank page... Bizarre...