HTML markup for a Logo

Whats the best coding practice?

[getxb]

I am bit confused here on what is the best practice for coding a logo. Options are:

1. <a class="logo" href="site_url" title="Some text" />
2. <a href="site_url" itle="Some text"><img src="logo_url" alt="Some text" title="Some text"/></a>
3. <div class="logo"><h1><a href="site_url" title="Some text"><img src="logo_url" alt="Some text" title="Some text" /></a></h1></div>
4. <div id="logo"><h1><a href="/">site_name</a></h1></div>

Kindly suggest.

[tedster]

#1 is not valid - there's no content for the <a> element.
#3 and #4 - forget using an H1 tag for the logo. An H1 should be specific to each page.

[getxb]

Thanks for your response. Shall I follow this thread? [webmasterworld.com]

[tedster]

Still looks accurate to me.