I'll have to re-read the TOS but I kinda remember is not allowed to mod, play or move the code in such ways. There is a thread around here where some members began inserting the Adsense code via JS include, I mean external file, not directly inserted on the page to avoid increasing the weight of the file.

Using CSS to move all your AdSense to the end of the page *may* improve your page load but most likely it'll hurt your income since the visitor might glance over the page and leave before any ads are displayed as options.

Don't fix what isn't broken.

i think i read a tip a long time ago that said if you want to target the ads better then you should surround it in the HTML code with the right words. so if you move the code to the end maybe your targeting will suffer.

i tried something like you are doing once and my earnings dipped a bit. not sure why, but i reckon it had something to do with the ad appearing before the rest of the page. a lot of people are still on dial-ups. if you make the ad appear slightly after the content, even if it's in the same location, then their eye will probably already focus on what they came to read rather than the ad