I'm having the same problems getting this 
first one:
you can choose your own color palette for gif (i.e. optimise the 256 available colors) and you can do this quite easily from flash. as Az sez a .bmp export will only be the first frame, and you'll still loose colors. you can export every frame individually as a series, and then relink them. provided they're sequentially numbered - they can be reimported as a series in most gif animation tools. there will not be any difference in quality. (between flash export to gif and image ready gif)
regarding the header - if you're working in php and html - just INCLUDE the page header - I presume you want a top menu bar - so either go the SSI router with a server side include
Code:
#include file="header.html"
- or just use php to do the same
Code:
<?php include ("head.html"); ?>
. why not have two divs or spans - one with fixed width so you know it will display the same regardless of res - and the other with no fixed width that will SPAN the rest of the page (hint hint)
this should be enough to get you started