I have had a little play (hope you don't mind) and have come up with a slightly modified header. I haven't spent long on it so it still needs changing to look the way I believe you wanted it to, but it should fit correctly in all browsers. I didn't have your images etc so I have improvised, but if you want me to go over it in more detail I will be free over the weekend to talk you through it or modify it for you. You can see the header at
Untitled Document or the code is below.
<div style="border:#CCCCCC 0px solid; width:900px;position:relative; left:50%;margin-left:-450px; margin-bottom:3px;">
<div style="width:900px; height:20px; background-color:#110268;"></div>
<div style="width:900px; height:10px; background-color:#FF0000;"></div>
<div style="width:900px; height:20px; background-color:#110268;"></div>
<div style="width:880px; background-color:#99DBEE; padding:10px;">
<p align="center">
<span style="font-family:Verdana;font-size:40px;line-height:1.20em;">Welcome To</span><br/><span style="font-family:Firenze SF; font-style:italic; font-weight:700;font-size:64.0px; line-height:1.13em; color:#ff0000; ">Brittany</span><span style="font-family:Firenze SF;font-style:italic; font-weight:700; font-size:64.0px; line-height:1.13em; color:#0000ff;">Guide</span><span class="Normal-C2"></span>
</p>
</div>
<div style="width:900px; height:40px; background-color:#030D81;">
<span style="font-family:Verdana; font-weight:700; font-size:24.0px;line-height:1.21em; color:#ffffff;"><a href="http://scripts.affiliatefuture.com/AFClick.asp?affiliateID=125093&merchantID=2922&programmeID=7750&mediaID=0&tracking=brittanyguide&url=" target="_blank" style="color:#ffffff;" title="ACCOMMODATION">ACCOMMODATION</a></span>
</div>
</div>
At this stage you should just explore a bit then it should start to make sense. As a first site not a bad one. Where possible use divs as they load quicker than tables, and setting HTML,BODY,TD,TABLE,DIV,P,FORM {margin:0px;padding:0px;} will remove all the default setting sizes of the browsers which will make it easier to make it look the same in different browsers.
Feel free to email me if you need any more help and as I said I will gladly go through it in detail over the weekend if you need it. I have my last exam tomorrow (1st year at uni) so after the celebrations of Friday night I'll be free.