Ok Annita,
I try to explain...
For your redirect, you should escape the question mark otherwise it will be taken in regular expression sense:
From URL: /ProdDetail.php\?ID=37
About the .htaccess file, that's what I mean. In some cases with a wrong URL, is Apache that return the error page (404 - Not Found). If you need to redirect these URLs using ReDJ, you can't do it. Just because ReDJ runs inside Joomla, but for these URLs, Apache doesn't pass the control to Joomla - it return the error by itself.
So, for these cases you can tell to Apache you want to manage the errors by yourself, specifying your custom error page. This is what ErrorDocument is for:
ErrorDocument 404 /
You are telling to Apache "everytime there's a wrong call with error 404 - Not Found, please pass the control to /", where there's is Joomla (and ReDJ) that can do the redirect.
I hope this was clear enough.
Regards,
Luigi