jquery dialogs do not work in quirks mode

I am writing a jquery based widget that will go on another company's website. When I try to set the height of the dialog via $('#dialog').height(450), it sets the dialog to be much shorter. I'm able to get it to be 380px high by using 380, but setting it to 381 makes the dialog 1 pixel high. I've determined that the bug happens only in IE8 in quirks mode. Yes, I know jquery doesn't support quirks mode. I can't change the doctype, since it's not my website.

Even though what I did worked, I need to understand why. Is there a definitive guide to how jquery works in quirks mode?