Banner Ads on bottom of different apps- Is this a Virus? I have Android 4.4.2. On a couple of apps (like Huffington Post and NBC 4 LA)I've noticed different banner ads that appear on the bottom of the screen inside different apps. The thing is these banner adds on the bottom of the page look very similar. I don't know if these apps use the same advertising company or what the situtation is. They're right on the bottom of the page so when you're scrolling you often hit them when I don't want to. 

Are these normal or do i have a virus that installs adds inside some of my apps on my phone? 

EDIT: I've added an image of the type of ad. This type of banner ad appears on the bottom of the screen inside different apps on my phone. Is this normal?
There are various advertising networks that will use cookies and the likes of which to track you and profile your online movement, and then later use those to target ads at you. It is possible that the NBC and Huffington Post Apps are using the same avertising network and thus showing the same/similar adverts.

You might want to check out adblockplus for android, it no longer requires root access and their installation instructions are quite easy to follow.