Jim, you cannot use HTML like that to change the Theme items. The Theme will strip away HTML code as a security. There are some nasty people around who would inject code and damage your site (although this is a general principle and unlikely to happen in development mode). Think about a Contact Form - that's a classic target.
When you develop your Pages, use it by all means and I'd recommend you look up Twitter Bootstrap 2 as this will give you a lot of features you may need. Customizr has been designed to get the most out of TB2.
Can you describe your problem (not solution) so we can understand what you're trying to achieve. Most problems can be overcome by using either CSS in the CustomCSS Panel or child theme, or with php code (more complex for a newbie).