IE8 in non-compatability view, Version 8.0.6001.18702
The code below represents the problem:
<body><div style="height:400px;width:400px"><iframe src="http://mail.ru" height="100%" width="100%"></iframe></div></body>
Scroll the IFRAME to the right to the middle of "Скачать Спутник с музыкой" orange label.
Alt-Tab to other window and Alt-Tab back to IE window.
The internal HTML will appear ouside of IFRAME boundaries.
Screenshot demonstrating the problem: 
Does the IFRAME rendering have a bug?
May be I have an unpatched version (automatic updates are turned ON).
Could you suggest a workaround except turning on Compatability View?