I am trying to develop simple popup footnotes for a web site I manage. I have it working in a test page. The behavior desired is that the popup appears when the mouse hovers over the footnote number in the text. There is a "close" link inside the popup, and when dismissed, the page behind it should be exactly as it was before the popup was shown. BUT ... I initially noticed that when I dismiss the popup in a broader test of some actual documents from the site, the browser jumps back to the top of the web page. It took me quite a while to discover that the correctly working initial test page has !DOCTYPE XHTML 1.0, whereas the pages from the site are !DOCTYPE html ie HTML5. I can reproduce this at will.