i can't open a web page

Hello,

This is my problem: i can't open a web page, when i try, a message says: connexion impossible, please check your internet parameter.
But i don't know what souhld i change... i try to switch of my firewall but it doesn't come from here.
I use firefox and vista.
If somebody can help me it could be great
Thank you

PS: can pspad open all types of web page?

program settings / Internet