Right, at the moment you your URL parameter has a name of 1
So your link, from the referrer page would be
You can change the name of the URL parameter, from 1, to something like 'cat' so it would read
On the categories page (the page that lists your categories) the anchor text or image for that category needs to have that link above, containing the URL parameter and the value that it is passing. That is so the recordset filter you applied can pick up the information it needs to filter the data.