Your looking at something called micro-bubbles. These are what skimmers spit out, and if its a HOB
filter, chances are the return pipe is going directly in to your tank, hence the bubbles you see. Honestly, my skimmer did this for the first week or so, and then the micro-bubbles ceased to an almost undetectable level. However, if you feel you can't take it much longer, and that it is getting on your last nerve, usually fitting a sponge in the return section of the skimmer will help to eliminate a large amount of micro-bubbles.
As you can see on this picture here:
there is a black sponge on the return pipe that not only acts as a filter, but works to eliminate bubbles as well. There should also be another sponge that sits in the return compartment to yet again, aid in filtration and the reduction of bubbles going back in to the display.