I've recently started using DynamicWP's Simple White Theme.  The theme is excellent, but generated around 60 validation errors.  Luckily these were caused by a scant half dozen errors in the source code.

Here is a quick summary of the errors, why they need to be fixed, and how to fix them.

footer.php - line 8

Why: Target isn't a valid XHTML attribute

From:

<p>Powered by <a href="http://www.wordpress.org/" target="_blank"WordPress</a> | SimpleWhite by <a href="http://www.dynamicwp.net/">Dynamicwp</a></p>

To:

<p>Powered by <a href="http://www.wordpress.org/" >WordPress</a> | SimpleWhite by <a href="http://www.dynamicwp.net/">Dynamicwp</a></p>

index.php - line 63

Why: The & symbol should be escaped to & when used in URLs. The element needs to be closed. The alt attribute needs to be included.

From:

<img src="<?php bloginfo('template_directory'); ?>/timthumb.php?src=<?php echo catch_that_image(); ?>&w=275&h=120&zc=1">

To:

<img src="<?php bloginfo('template_directory'); ?>/timthumb.php?src=<?php echo catch_that_image(); ?>&amp;w=275&amp;h=120&amp;zc=1" alt="" />

line 69

Why: The element needs to be closed

From:

<hr>

To:

<hr />

sidebar.php - line 24

Why: The element needs to be closed

From:

<img src="<?php echo catch_that_image(); ?>">

To:

<img src="<?php echo catch_that_image(); ?>" />

line 26

Why: The & symbol should be escaped to & when used in URLs. The element needs to be closed. The alt attribute needs to be included.

From:

<img src="<?php bloginfo('template_directory'); ?>/timthumb.php?src=<?php echo catch_that_image(); ?>&w=40&h=40&zc=1">

To:

<img src="<?php bloginfo('template_directory'); ?>/timthumb.php?src=<?php echo catch_that_image(); ?>&amp;w=40&amp;h=40&amp;zc=1" alt="" />

line 29

Why: The alt attribute needs to be included.

From:

<img src="<?php bloginfo('template_directory'); ?>/images/noimagesmall.jpg" />

To:

<img src="<?php bloginfo('template_directory'); ?>/images/noimagesmall.jpg" alt="" />

line 42

Why: Error.  The <ul> should be </ul> to close the list.

From:

<ul>

To:

</ul>