I would imagine this is likely being caused by the URL if you are showing that.  URL's can get very long, and if they do not have any spaces in them, they will not wrap and will stretch the page out.  That goes for images and other type of text that the browser can't figure out how to wrap. 

The easiest thing would likely be to not show the URL field.  I think you might be able to limit the number of characters shown in the XSL style sheet for the URL if you really wanted to show it.  Another option might be to try and make it show up inside a div that can scroll horizontally.  That could get somewhat ugly, but at least your entire page wouldn't stretch.