How not to enter IE quirks mode?

How not to enter IE quirks mode?

Hello,

Im trying to assign some css in jquery, I thought it wasnt working but I found out about "quirks mode" in IE.

How can I prevent IE from entering quirks mode? Or put it in IE 9 mode ...(Why am I even having to ask this question?) 

Ive tried the 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"  "http://www.w3.
rg/TR/xhtml1/DTD/xhtml1-transitional.dtd">  , 

I had to use that to fix a datepicker issue, but it didnt put it in IE 9 mode.