If your site design is based on absolutely positioned divs with a fixed height, then the size of the content area can't adjust when a longer IDX page, like a results page, is loaded. To add an interior scrollbar in these cases, rather than allow the cutoff or visible overflow, go to Customize --> Global HTML Wrapper, and find the opening div tag for your primary content area. This will usually be toward the end of the Global Header Code section. Within it, add this code:
style="overflow:auto;"
Save your changes and refresh an IDX page to test.