Each selected retail site's results will show in a separate window. Depending on the browser you are using and how you have configured it, these may be actual windows or may be tabs. And, of course, if you have configured the browser to disallow the programmatic opening of new windows, nothing will happen!
If the retail site allows customization of the results and on the response to clicking on a result link, these customizations will remain under your control. This page makes no attempt to influence any of those custom choices.
To add a new site, it must be of a type that shows the search URL in the address bar. For example, to add circuitcity.com as a new retail resource, visit www.circuitcity.com, enter a search term such as 'dvd cable' and initiate the search. Now, check the address bar. It will show something like http://www.circuitcity.com/applications/SearchTools/search.asp?keywords=dvd+cable&searchbtn.x=0&searchbtn.y=0 Copy it. Now, return to this web page and click the 'New Searcher' button. In the new 'Default URL' field that shows up, paste the copied address. Next, delete everything except the search term and then replace the search term with #product#. The result should look like http://www.circuitcity.com/applications/SearchTools/search.asp?keywords=#product#
Finally, click the 'Save Customizations' button to save the result.