Probes do content checking very well, and its an important measure on if a page is responding with content that you want and not some error page. However, when you setup a probe to do content checking, it is important that that you follow these guidelines:
1. Only do content checking on a direct URL. Content checks will not work on a redirect.
3. Keep it simple, if you are testing for content on a login page, maybe test for something like: XYZ Company Login.
4. Content checks are character sensitive.
5. Try to avoid using special characters.