In July 2006, Counter-Strike Maps owner Shawn Olson posted an article relating to Counter-Strike not being able to access servers after upgrading to Internet Explorer 7.

There is now a solution that has been posted on the Steam Forums.

Essentially, you must add a Registry Entry which is spelled out below:

You can also download a zip file with that entry below. Open the zip file, copy to your computer and open the file. Windows will give a prompt asking if you really want to add the information to the registry. Hit "Yes".

After adding this you will be able to play Counter-Strike with Internet Explorer 7.