More edits to TwentyTen Theme

There are a couple of edits I’d like to make that I’m having an issue with:

1. I’d like to set a specific location for my menu bar. Visually I want it to look centered but I’d like to do it manually by editing the margin to the left. Right now I have:

#access {
width: 800px;
display:block;
position: absolute;
margin-left: 260px;
margin-top: 200px;
}

But it’s not doing anything.

2. I’d like to add more spacing in between each menu item on the navigation
3. How do you add more space on the very bottom of the page in between “older posts” and the bottom of the page?
4. How do I make the tags and leave a comment rollovers match my date stamp rollover?