I have not seen style sheet links like this before what is the ?3 specifying... does anybody have a link to something that explains this?

It's a php script that is causing the ?3 on the end. The use of this 3 could be unlimited in scope. It doesn't actually affect the stylesheet, so I wouldn't worry about it.

No.

It seems to be some type of specifier for a unique css sheet.. instead of using different names.. the ?3 seems to specify an import or addition to the style sheet. I can see it when I view the source of a webpage.

They must have multiple style sheets there where users can switch them. Maybe change colors or font sizes...