Empty Location header can cause unpredictable behaviour
If you specify a blank location HTTP header then you can expect different behaviour between browsers.
Take the following PHP code for example:
header( "Location: " );
In Internet Explorer, a blank location will redirect the user to the root of the current folder ("./"). In Firefox, the user is not redirected at all.
ASP is a little smarter in that
Response.Redirect("") will give you an error message indicating that you're missing the URL. Although, you can duplicate the redirection problem with the following code:
Response.Status="302 Moved Permanently" Response.AddHeader "Location", ""
Why is this an issue? Specifically, if you're using variables for redirection and the variable is empty or null then you will run into this problem. If you wanted it to redirect to the root of the current folder then the error may not be evident until you tested in something other than Internet Explorer.