Summary
The WebLink 10 back-end is significantly different from the WebLink 9 back-end. This may break some of your more advanced customizations for the search page. To continue using the WebLink 9 search page after upgrading to WebLink 10, you can use the Search9.aspx file in the WebLink installation folder.
To use the WebLink 9 search page
Your WebLink 9 search page customizations should now work as they used to.