Having happily taken Paul's advice and switched to a fixed width design, it seemed like I was getting there. Save for some text spacing issues and horizontal placement of buttons (neither issue fully addressed so far) my design looks fine in IE6 and Opera7. I guess I should have tried Mozilla Firefox earlier. Virtually everything is missing. Where, oh where have I gone wrong?

CSS Code:
html, body {
background-color: #50519d;
font-size: 12px;
font-family: Verdana, Arial, Helvetica, sans-serif;
text-align: center;
margin: 0;
padding: 0;
}
h1, h2, h3, h4 {
text-align: center;
margin-top: 0px;
padding-top: 0px;
clear: both;
}
div#fullwrap {
width: 750px;
position: relative;
margin-left: auto;
margin-right: auto;
top: 10px;
}

div#header {
position: absolute;
width: 750px;
height: 100px;
top: 20px;
left: 0px;
text-align: center;
}

#header img {
width: 712px;
height: 70px;
border-style: ridge;
border-color: #e6edff;
border-width: 5px;
}
.thinline {
line-height: 1.2em;
}

div#columns {
position: relative;
width: 750px;
top: 110px;
background-color: #fffae6;
}

div#main {
float: left;
width: 480px;
top: 0px;
left: 0px;
background-color: #ffe480;
padding: 10px;
}

div#main1 {
margin-left: 1px;
margin-top: 1px;
margin-right: 1px;
margin-bottom: 1px;
}

div#main2 {text-align: left;}

div#main2-sample1, #main2-sample2, #main2-sample3 {
float: left;
width: 130px;
height: 205px;
padding-top: 15px;
background-color: #ffffff;
border: 1px solid #000000;
text-align: center;
margin-left: 2%;
margin-bottom: 5px;
display:inline;/*ie fix*/
}
div#main2-sample2 {
background color: #ffc2ff;
}
div#main2-sample3 {
background color: #d6ffff;
}
div#main3 {
margin-left: 1px;
margin-top: 1px;
margin-right: 1px;
margin-bottom: 1px;
}
div#main3 ul {
margin: 5px;
padding: 0px;
font-family: Arial, Helvetica, sans-serif;
font-size: small;
color: #000;
line-height: 30px;
text-align: center;
}
div#main3 li {
list-style-type: none;
display: inline;
}
div#main3 li a {
text-decoration: none;
padding: 7px 10px;
color: #000;
}
div#main3 lia:link {
color: #000:
}
div#main3 lia:visited {
color: #CCC;
}
div#main3 lia:hover {
font-weight: bold;
color: #000;
background-color: #3366FF;
}
div#main4 {
margin-left: 1px;
margin-top: 1px;
margin-right: 1px;
margin-bottom: 1px;
}
div#main5 {
margin-left: 1px;
margin-top: 1px;
margin-right: 1px;
margin-bottom: 1px;
clear: both;
}

div#nav {
float: right;
width: 210px;
top: 0px;
left: 490px;
padding: 5px;
background-color: #fffae6;
}

div#nav ul {
margin: 5px;
padding: 0px;
font-family: Arial, Helvetica, sans-serif;
font-size: small;
color: #000;
line-height: 30px;
text-align: left;
}
div#nav li {
list-style-type: none;
}
div#nav li a {
text-decoration: none;
padding: 7px 10px;
color: #000;
}
div#nav lia:link {
color: #000:
}
div#nav lia:visited {
color: #CCC;
}
div#nav lia:hover {
font-weight: bold;
color: #000;
background-color: #3366FF;
}

div#footer {
position: relative;
width: 720px;
clear both;
margin-top: 100px;
padding: 15px;
background-color: #fffae6;
}

img#flowers{
float: right;
width: 200px;
height:280px;
margin:5px;
}

img#fwlogo{
margin-left: 5px;
margin-right: 5px;
margin-bottom: 30px;
}
img#ftdlogo{
margin-left: 25px;
margin-right: 35px;
margin-bottom: 15px;
}
img#fpologo{
margin-left: 25px;
margin-right: 35px;
margin-bottom: 30px;
}

img#main2_im1{
width: 100px;
height: 116px;
}
img#main2_im2{
width: 100px;
height: 116px;
}
img#main2_im3{
width: 100px;
height: 116px;
}


/*CSS for button divs*/
div#buttonA {
margin-top: 15px;
margin-bottom: 30px;
}
div#buttonb, div#buttonc, div#buttond, div#buttone {
float: left;
margin-top: 15px;
margin-left: 2%;
margin-bottom: 30px;
}
div#buttone {
clear: both;
}
div#buttonA ul, div#bottonc ul, div#bottond ul, div#bottone ul, {
margin: 0px;
padding: 10px;
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 14px;
line-height: 30px;
}
div#buttonb ul {
margin: 0px;
padding: 10px;
font-family: Verdana, Arial, Helvetica, sans-serif;
font-size: 13px;
line-height: 30px;
}
div#buttonA li, div#buttonb li, div#buttonc li, div#buttond li, div#buttone li {
list-style-type: none;
height: 30px;
margin: 5px;
text-align:center;
}
div#buttonA li {
width: 180px;
}
div#buttonb li, div#buttonc li, div#buttond li, div#buttone li {
width: 400px;
}
div#buttonA li a, div#buttonb li a, div#buttonc li a, div#buttond li a, div#buttone li a {
text-decoration: none;
display: block;
background-color: #839dff;
border-style: solid;
border-bottom-color: #717a9f;
border-right-color: #6276bf;
border-left-color: #c1ceff;
border-top-color: #cbebff;
}
div#buttonA li a:link, div#buttonb li a:link, div#buttonc li a:link, div#buttond li a:link, div#buttone li a:link {
color: #000000;
font-weight: bold;
background-color: #839dff;
border-style: solid;
border-bottom-color: #717a9f;
border-right-color: #6276bf;
border-left-color: #c1ceff;
border-top-color: #cbebff;
}
div#buttonA li a:visited, div#buttonb li a:visited, div#buttonc li a:visited, div#buttond li a:visited, div#buttone li a:visited {
color: #000000;
font-weight: normal;
background-color: #839dff;
border-style: solid;
border-bottom-color: #717a9f;
border-right-color: #6276bf;
border-left-color: #c1ceff;
border-top-color: #cbebff;
}
div#buttonA li a:hover, div#buttonb li a:hover, div#buttonc li a:hover, div#buttond li a:hover, div#buttone li a:hover {
font-weight: bold;
color: #FFFFFF;
background-color: #414e80;
border-style: solid;
border-right-color: #c1ceff;
border-bottom-color: #cbebff;
border-top-color: #717a9f;
border-left-color: #6276bf;
}
div#buttonA li a:active, div#buttonb li a:active, div#buttonc li a:active, div#buttonb li d:active, div#buttone li a:active {
font-weight: bold;
color: #FFFFFF;
background-color: #717a9f;
border-style: solid;
border-right-color: #c1ceff;
border-bottom-color: #cbebff;
border-top-color: #717a9f;
border-left-color: #6276bf;
}



HTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

<head>
<title>Flower delivery in Canada by Floraworld, the all-Canadian online order service</TITLE>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta name="Description" content="Flower delivery in Canada and beyond. Order online or by phone (1-888-ROSE-888) to send flowers through FloraWorld, a Canadian company with a proven network of local florists affiliated with FTD, Teleflora and Grower Direct. Same day delivery on early orders. Aeroplan points or CAA discounts on eligible orders. Fresh flowers, roses, arrangements and gifts. Satisfaction Guaranteed" />
<meta name="Keywords" content="Flower delivery in Canada, online order, 1-888-ROSE-888, send flowers, Canadian, florist, FTD, Teleflora, Grower Direct, Aeroplan, CAA, roses, arrangements, gifts" />
<meta name="Robots" content="all" />
<link rel="stylesheet" type="text/css" href="floraca-style.css" />
</head>

<body>
<div id="fullwrap">
<div id="header"><img alt="floraworld 1-888-rose-888" src="images/FWca_header3.gif" />
</div>

<div id="columns">
<div id="main">
<div id="main1">
<h2>Flower Delivery in Canada</h2>
<h3>Let Floraworld Deliver Your Floral Message</h3>
<img id="flowers" src="images/covermain.jpg" alt="flowers delivered" />

<p>Send flowers<br />
across Canada, the USA, and worldwide<br />
through our network of selected<br />
local FTD and Teleflora florists.</p>
<p>Floraworld offers/p>
<p>&nbsp &nbsp -- easy, secure online ordering</p>
<p>&nbsp &nbsp -- fast, reliable floral delivery<br />
&nbsp &nbsp &nbsp &nbsp (same day delivery on early orders)</p>
<p>&nbsp &nbsp -- Aeroplan Miles (or CAA Discount)<br />
&nbsp &nbsp &nbsp &nbsp with every eligible order</p>
<p>&nbsp &nbsp -- the freshest roses and other <br />
&nbsp &nbsp &nbsp &nbsp cut flowers in exquisite bouquets <br />
&nbsp &nbsp &nbsp &nbsp and arrangements</p>
<br />
<br />
<p>Select one of the Favourites on this page or<br />
see a wider selection in our main catalogue.</p>
<br />
<br />
</div>

<div id="main2">
<h2>Popular Selections for Delivery in Canada</h2>
<div id="main2-sample1"><img id="main2_im1" src="images/tnB18-3226.jpg" alt="FTD Basket of Stars Bouquet" />
<p>Basket of Stars Bouquet</p>
<p>$73.95 (CDN)</p>
</div>

<div id="main2-sample2"><img id="main2_1m2" src="images/tnB20-3266.jpg" alt="FTD Pink Opulence Bouquet" />
<p>Pink Opulence Bouquet</p>
<p>$69.95 (CDN)</p>
</div>

<div id="main2-sample3"><img id="main2_im3" src="images/tnC4-3085.jpg" alt="FTD Many Thanks Bouquet" />
<p>Many Thanks Bouquet</p>
<p>$112.95 (CDN)</p>
</div>

<br />

<div id="buttonb">
<ul>
<li><a href="link1.html">View the Entire FloraWorld Catalogue</a></li>
</ul>
</div>
<br />
<br />
</div>

<div id="main3">
<h2>Canadian Flower Delivery</h2>
<h3>Favourite Places to Send Flowers in Canada</h3>
<ul>
<li><a href="link1.html">Victoria, British Columbia</a></li>
<li><a href="link2.html">Vancouver BC</a></li>
<li><a href="link3.html">Kelowna BC</a></li>
</ul>
<ul>
<li><a href="link4.html">Edmonton, Alberta</a></li>
<li><a href="link5.html">Calgary, Alberta</a></li>
<li><a href="link6.html">Regina, Saskachewan</a></li>
</ul>
<ul>
<li><a href="link7.html">Saskatoon, Saskatchewan</a></li>
<li><a href="link8.html">Winnipeg, Manitoba</a></li>
<li><a href="link9.html">Toronto, Ontario</a></li>
</ul>
<ul>
<li><a href="link10.html">Ottawa, Ontario</a></li>
<li><a href="link11.html">Montreal, Quebec</a></li>
<li><a href="link12.html">Moncton, New Brunswick</a></li>
</ul>
<ul>
<li><a href="link13.html">Saint John, New Brunswick</a></li>
<li><a href="link14.html">Halifax, Nova Scotia</a></li>
<li><a href="link15.html">Charlottetown, PEI</a></li>
</ul>
<ul>
<li><a href="link16.html">St. Johns, Newfoundland</a></li>
<li><a href="link17.html">Yellowknife, NWT</a></li>
<li><a href="link18.html">Whitehorse, Yukon</a></li>
</ul>
<ul>
<li><a href="link19.html">All Other Canadian Locations</a></li>
</ul>

<div id="buttonc">
<ul>
<li><a href="link1.html">&nbsp &nbsp ORDER FLOWERS NOW &nbsp &nbsp</a></li>
</ul>
</div>
</div>
<br />
<br />
<br />
<div id="main4">
<br />
<br />
<h2>U.S.A. Flower Delivery</h2>
<h3>Popular Places to Send Flowers in the United States</h3>
<div id="buttond">
<ul>
<li><a href="link1.html">For Flower Delivery in the USA, CLICK HERE</a></li>
</ul>
</div>
</div>

<div id="main5">
<br />
<br />
<h2>International Flower Delivery</h2>
<h3>Popular Places to Send Flowers around the World</h3>
<div id="buttone">
<ul>
<li><a href="link1.html">To Order Flowers for International Delivery, CLICK HERE</a></li>
</ul>
<br />
<br />
</div>
</div>

</div>

<div id="nav">
<br />
<br />
<img id="fwlogo" src="images/flora_logo.gif" alt="FloraWorld" />
<br />
<div id="buttonA">
<ul>
<li><a href="link1.html">Order Flowers Now</a></li>
</ul>
</div>

<h4>Flower Occasions</h4>
<ul>
<li><a href="link31.html">Anniversary Flowers</a></li>
<li><a href="link32.html">Birthday Flowers</a></li>
<li><a href="link33.html">Congratulations Flowers</a></li>
<li><a href="link34.html">Get Well Flowers</a></li>
<li><a href="link35.html">New Baby Flowers</a></li>
<li><a href="link36.html">Sympathy Flowers</a></li>
<li><a href="link37.html">Funeral Flowers</a></li>
<li><a href="link38.html">Christmas Arrangements</a></li>
<li><a href="link39.html">Easter/Passover Flowers</a></li>
<li><a href="link40.html">"I Love You" Flowers</a></li>
<li><a href="link41.html">Mothers Day Flowers</a></li>
<li><a href="link42.html">Valentines Day Flowers</a></li>
</ul>
<br />
<img id="ftdlogo" src="images/ftdlogo.jpg" alt="FTD" />
<img id="fpologo" src="images/fpo_logo2.jpg" alt="Flower Promotion Organization" />
<br />
<h4>Useful Flower Facts<br /> & More</h4>
<ul>
<li><a href="link1.html">Flower Care</a></li>
<li><a href="link2.html">Flower Holidays</a></li>
<li><a href="link3.html">Meaning of Roses and Flowers</a></li>
<li><a href="link5.html">Monthly Flower Charts</a></li>
<li><a href="link6.html">Monthly Birth Stones</a></li>
<li><a href="link8.html">Flower Reminder Service</a></li>
</ul>
<br />
<br />
</div>
</div>
<div id="footer">
<p>Floraworld 1-888-ROSE-888 (1-888-767-3888) &nbsp &nbsp &nbsp &nbsp &nbsp |&nbsp
&nbsp &nbsp &nbsp &nbsp &nbsp; Site Map &nbsp &nbsp &nbsp &nbsp &nbsp &nbsp|&nbsp
&nbsp &nbsp &nbsp &nbsp &nbsp Contact Us</p>
</div>
</div>
</body>
</html>


I see from recent posts that I am not the only one having Firefox problems.
I now realize the value of testing early in Firefox and hereby undertake to change my ways
Thanks for any and all help.
regards,
Cam