Does spider ignore 'hidden' divs?

So I plan on having a 'div' element at the very top of my page with a load of relevant links and content - however I want to move the innerHtml of this div to another div at page-load time using javascript.

My question is...is there anyting wrong with this? Google should ignore the javascript onload event....and should also ignore the display:none css attribute....thinking that the content at the top is visible right?

There is no problem if there is a natural and logical way for visitors to make the hidden content visible on demand (with an onclick or onmouseover event or any other way that benefits to the visitor experience).

IT WILL BE A PROBLEM if the hidden div is just a way to hide content to visitors.

What you are describing is search engine spam - pure and simple. You are placing content at the top of your page FOR SEARCH ENGINES ONLY. You are hiding it from users and using JavaScript to move it elsewhere. That is spam (showing SEs 1 thing and users something different for the sole purpose of ranking better.

Regarding your statement that Google should ignore your onload event - who says? If a browser can interpret it (ever use the view generated source function in the FF Web Developer addon) why do you assume Google can't? I would NOT make that assumption. But, even if it is true, a human viewer will see it in a second, and will see it's intent. Googel does have humans that review sites.

Bottom line, it is against Google's Webmaster Guidelines. It is considered SE spam and it may be punished if caught. Will you get caught? Maybe, maybe not.