There are many possible reasons this is happening and the contributing factors vary for every individual computer.
Start by clearing old files and settings may be preventing you from connecting to the Internet.
Click on Tools.
Select Internet Options.
Click the General tab.
Click the Delete Files button.
When the box opens, put a check in Delete All Offline Content.
Click Delete Cookies. When you are prompted to confirm this selection, click Okay.
Click View Objects.
Click View, and then click Details.
If Damaged appears in the Status column for any program file, remove that program file.
Close the Downloaded Program Files dialog box.
In the Settings dialog box, click OK .
Under History, click Clear History, and then click Yes when you are prompted to confirm the selection.
In the Internet Options dialog box, click Okay.
Try to browse the Internet.
If no joy, lets see if we can try and repair the internet connection.
Try running Winsock XP fix
This utility can fix tricky most connection problems.
See if there is anything in this Micro$oft Article that helps: Page Cannot be Displayed