Make the tables border less. Make the site total white. move the rectangle ad inside the text not under the images. Make all pages same color. and if possible rename the html files with "-" not "_" . Make the table centered. good luck.
Personally Im not a fan of Black and bright green. This would be the first thing. People looking for help with gout prolly wouldnt want to go to a dark and dingy website either. I think medical sites could do with being bright & happy
unfortunately, poor design, too adsense ads, it's even not centered (in resolution 1680 x 1050 it doesn't looks good), sorry
Almost every members suggested you to change the color of your website escpecially background. I know adsense is an another source of generating revenue but too much usage of the same would kill your website's subject/target. So reduce a bit. I can see your website got lots of content for the users (hopefully not copied ). Keep updating, this is any of the website's most strong point. Best of luck