So I was playing with SharePoint search a while back, and I was wanting to display some results differently based upon what type of item the result was for.
It turns out that there is a node in the results xml file that shows this – ContentClass :
As you can see, the first highlighted result is STS_ListItem_DocumentLibrary. Pretty clear what that is. Not all results actually have a content class – the second highlighted result is from a document on a file share, and it doesn’t have a ContentClass.
So what content classes are there? Well, Dan Attis has a good list, along with a caveat about Welcome pages in the results. There is a similar list here. (Nobody mentions not having a ContentClass though). But unfortunately, I don’t know how to add new content classes