hi bjoshi,

Welcome to the forums.
For Google adsense you can use the plugin.
Other things like something personalized should be added to the post and that should either work or give an error like No Valid XHTML. This depends a bit, Flash things are often <embedded> and that will never validate.

You could also hack your skin. Find skins/YOURSKIN/index.main.php or skins/YOURSKIN/posts.main.php depending on the skin and search for the posts loop that starts like this:

		while( $Item = & mainlist_get_item() )
		{	// For each blog post, do everything below up to the closing curly brace "}"
		?>

and ends like this:

		</div>
		<?php
		locale_restore_previous();	// Restore previous locale (Blog locale)
		}
	?>

You can add a banner at the beginning or at the end and it will show up in every post.

Good luck

Thanks for that.
I'm not getting any errors at present. It saves normally, just doesn't show it.
What if I want to have different banners etc in different posts? using the index.php file I can only ever have one banner right?