Banner vs. Description Styles

I had a problem trying to get the "building" link to display correctly in the description. The banner has is an "id" style and the description is a "class". The style for the link kept being picked up from the banner and not the description style in the stylesheet. (Too big!)

I had to eliminate the "span" from all templates replacing it with its own "div", changing this:

<div id="banner">
<h1><a href="<$MTBlogURL$>" accesskey="1"><$MTBlogName$></a></h1>
<span class="description"><$MTBlogDescription$></span>
</div>

to this:

<div id="banner">
<a href="<$MTBlogURL$>" accesskey="1"><$MTBlogName$></a>
</div>
<div class="description"><$MTBlogDescription$></div>

By removing the span tag, the link I created in the description (building) would adopt the correct style. Otherwise, it kept picking up the banner style. I don't understand the difference between "id=" and "class=".... something to study.