Once the user logs in, the &cat_ID=3 is lost from the end of the querystring and the page he is sent to (readreport.asp) ends up with an error.
How can I get around this problem? If the user is already logged in, the target page comes up fine - no part of the querystring is lost. So, the problem seems to be occuring on the login.asp page.
it's because technically once the querystring encounters an & it's a new querystring variable, therefore, not part of target anymore. how are you redirecting to login.asp? is it in your readreport.asp code or are you using inc_header in that file?