Hi davidharvey,
I actually went through this same thing (all about syntax) with the second site I did, and craigteel actually pointed out that syntax just isn’t what it was now that we’re in the HTML5 era. Here’s the thread, which links to a good article. http://forum.webflow.com/t/not-quite-finished-but-looking-for-some-feedback/5923/11
I have been more careful since, regardless, though, so thanks for pointing it out!