American FactFinder: Why did some of my selections disappear from the “Your Selections” box in Advanced Search?
Most likely, your selections were removed because:
As noted at the top of each table view page, you must use the "Back to Search Results" button to return to the Search Results page. At the Search Results page you can update/modify "Your Selections." Since the Table Viewer page is based on "Your Selections" and is not a static web page, using your browser's "Back" button will likely result in items being removed as it returns to the previous static page you visited in the American FactFinder site.
If you have been inactive on the site for more than 30 minutes a pop up will appear and your session will restart which will result in items being removed from “Your Selections.”