It is an javascript trick to change the background color of ur site[this will work if ur site doesnt have background image]
for example
change background:

BlackWhiteLightgray getcode:
<br/>change background: <form method="get" action=""><input type="hidden" name="PHPSESSID" value="2e2c56c6d1b48010e904e55ceda08ff6" /><select name="userstyle_set"><option value="#000000,#FFFFFF,#FFFFFF" >Black</option><option value="#ffffff,#483d8b,#483d8b" >White</option><option value="lightgray,#483d8b,#483d8b" >Lightgray</option></select><input type="submit" value="Change!"/></form> main

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