Today I found out that if you don't want to do any sort of modifications to adjust your site for IE8, you don't have to do that. It isn't ideal situation of course, but there definitely could be circumstances where this could be necessary; for instance, web developer got fired. 
The following tag will make this happen:
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
It will display standards DOCTYPEs in IE7 Standards mode and quirks DOCTYPEs in Quirks mode.
More info about this is available on MSDN website.