Use SubAccounts to track sales from specific pages within your site.
For example if you have 3 GigaCash™ links on 3 different pages within your site, you could use a different SubAccount value for each of those 3 links, allowing you to track sales from each page.
To specify your own SubAccount, simply change 'gcsa=default' to your specific page name ( e.g. gcsa=yourpage1 )