[carterdea]

What about an ID for main page elements and things that never will change like #header or #footer or #sidebar?

[jarin]

Ideally for those you would use the html5 header, footer, and aside tags, respectively. You can use the html5 Javascript shim to enable support for those tags in IE.

[job45]

sidebar is not equal aside, and you can have several headers footers on one page.