Here's a simple block: <div> foo </div> This should be a code block, though: <div> foo </div> As should this: <div>foo</div> Now, nested: <div> <div> <div> foo </div> </div> </div> This should just be an HTML comment: <!-- Comment --> Multiline: <!-- Blah Blah --> Code block: <!-- Comment --> Just plain comment, with trailing spaces on the line: <!-- foo --> Code: <hr /> Hr's: <hr> <hr class="foo" id="bar">