alert can not show to normal

I download the new version 3.6. I would like to use the alert in new message function, I find the alert can not show to normal.

please help.
demo.rar (173 KB)

I find the problem between IE8 and IE 9,10.

IE9,10 can show correctly,

IE 8 can not show to correct.

please help,

Change doctype of the page like

With it, IE will render page in standard mode and message box will be correctly shown.