What's a hat tip?

A "hat tip" during the era when men used to wear hats was an acknowledgment or a non-verbal greeting. It was considered a polite gesture and it extended to  become a means to show respect and accreditation. In the early 2000's hat tip became an acknowledgement to someone (or a website) for bringing something to the blogger’s attention. Hat tip is also, sometimes, abbreviated as h/t or HT" (bloggossary.com). Hat tips also encourage a sense of community by allowing online members/bloggers to mention each other in a positive mannerHT Blogossary.com; Wisegeek.com.