can i put hidden keywords after my ad to target the demographics of my site? what about if its not hidden? will it even work and have relevant ads or still keep showing ads that have no relevance at all to my site or for the people who visit my site. i get 550k impressions a day and im making $55-$60 which is sad
You can't do this no - against their webmaster guidelines and a very sneaky tactic that undermines everyone else's efforts. Don't do it.
I sometimes put keywords in the alt tag for images that normall just get "", like dividers and spacers. I don't do it every time, but sometimes, and only for relevant keywords to the page. Normally when I do this it's because the page is showing some funky adsense that has nothing to do with the content.