Types of Content - Search scope Rule

There are a set of pre-defined values Sharepoint assigns to the property contentClass to represent different types of content. The table below has most of them.

STS_Document
STS_List_Comments
STS_List_300
STS_List_Contacts
STS_List_850
STS_List_DiscussionBoard
STS_List_Announcements
STS_List_DocumentLibrary
STS_List_Categories
STS_List_Events
STS_List_GenericList
STS_list_Links
STS_List_PictureLibrary
STS_List_Posts
STS_List_Tasks
STS_ListItem_300
STS_ListItem_850
STS_ListItem_Announcements
STS_ListItem_Categories
STS_ListItem_Comments
STS_ListItem_Contacts
STS_ListItem_DiscussionBoard
STS_ListItem_DocumentLibrary
STS_ListItem_Events
STS_ListItem_GenericList
STS_ListItem_Links
STS_ListItem_Posts
STS_Site
STS_Web