It's best to set your doctype to the max
<!DOCTYPE html>
And use the meta tag to change certain pages.
The meta tag is placed in the head
tag and tells your browser how to behave.
For IE 8
<meta http-equiv="X-UA-Compatible" content="IE=8" />
For Quirk mode never tried it myself, so I'm not sure how it will work
<meta http-equiv="X-UA-Compatible" content="IE=5" />
Setting it to 5
supposedly tells the browser to work in quirks mode.