encyclo - 11:17 am on Nov 22, 2007 (gmt 0)

An image is an inline element, so it needs to be wrapped in a block element to validate, either a div or paragraph will do:

<h1 id="header">
[b]<p>[/b]<img src="wp-content/themes/boogy/images/ys-logo.gif" width="180" class="logo" alt="boogy Logo" />[b]</p>[/b]
<div id="flashcontent" class="adobe">

You may need to adjust the margins if you use a paragraph.