That is more than likely linked to a template/css change you've made elsewhere.
Have you got a link to your site?
The actual code for that is:
Code:
<div id="mce_2" class="editorInlinePopup" style="width: 355px; height: 127px; top: 1080px; left: 783px; z-index: 300001;">
Check the contents of editor_ui.css to see if anything has been set in there.