Ran into an interesting issue today at work, we had people randomly ending up in IE9 Quirks mode when viewing a page we’re developing. Since IE9 Quirks mode is pretty much useless, this was obviously causing some significant display issues. A bit of Googling revealed a solution (and a probably cause). Apparently in some cases having a:
Would cause IE9 to head straight into quirks mode. A simple fix is to place this in the <head> tag.
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
A question for anyone who actually comes across this – why even have IE9 Quirks Mode in the first place?