Exactly.
Here's an example of iWeb code from your site which I consider bloated and cross-platform incompatible:
HTML:
<div id="id3" style="height: 187px; left: 532px; position: absolute; top: 277px; width: 138px; z-index: 1; " class="style_SkipStroke_5">
<div class="text-content graphic_textbox_layout_style_default_External_138_187" style="padding: 0px; ">
<div class="graphic_textbox_layout_style_default">
<p style="padding-top: 0pt; " class="Caption">EDSGN 100 Section 12<br /></p>
<p class="Caption">Liz Kisenwether<br /></p>
<p class="Caption"><br /></p>
<p class="Caption">Teammates:<br /></p>
<p class="Caption">Jeremy Segermeister<br /></p>
<p class="Caption">Jen Healy<br /></p>
<p class="Caption">Dana Utembayeva<br /></p>
<p class="Caption">Jacob Walker<br /></p>
</div>
</div>
</div>
First off, the div has an id, class and style - all of which are perfectly legal but good developers merge into one id. This means presentation layer is 100% in the CSS file, and should not be integrated into the content layer as is here. Then you seeabsolute positioning for the div itself using z-indexing which isn't necessary for the simple layout based on what I saw in the browser. Different browsers apply CSS cascade effects and z-index differently, in a nutshell. Then, because you added in each line of text one at a time, iWeb didn't consolidate all the content into one P tag, for example. Each time another block level P tag is added, instead of simply putting the content in a simple DIV with an ID or class assigned the picture (with it's abolute positioning) will not be part of the document flow. And I guess adding a line break within a P tag is required if the CSS removes the default block level formatting of the P tag, but sure looks odd.
In short, confusing CSS, misuse of P tag, non-consolidated tags, heavy use of absolute positioning bypassing the document flow.
Of course everyone develops differently, so this is MY OPINION.
This is why coding by hand to create the basic layout and understanding how to properly position div's and grid out your design is really the key to making better, if not perfect, cross-platform compatible web sites.
I dare you to mention even some of this stuff to your teacher - heh.
-jim