I realize a skimmer is going to get dirty but is this normal???

http://i1280.photobucket.com/albums/...ps5znzlw46.jpg

http://i1280.photobucket.com/albums/...psqtsdezro.jpg

http://i1280.photobucket.com/albums/...psdlkwq8ut.jpg

This scum/dirt wipes off easy it comes back a couple days after I wipe it off, just wondering if this is normal or something I'm doing wrong with my pool water?
Thanks, Matt