Not every blog or site uses the footer. I wouldn’t go so far as to call it a mistake, just a wasted opportunity.
In creating a site we only have so much space available. There is the space which actually shows, the important, prime space. Then there are secondary areas like pages which give us a place to add more information. However, there is one area in between having the reader find and open a new page or giving prime space to information which isn’t vital (but necessary). The footer!
I found a great footer and took a screen capture to show it. My own footer is not so well planned out. No showcase among footers at the bottom of my site. It is a work in progress. I don’t even have all the various information which has been included in the footer at Richly Middle Class.