Not op but classless CSS frameworks are awesome. The idea is to keep it simple and use the appropriate HTML tags where there were generally meant to go, and the framework will theme the page to improve usability and add flair. I've developed some great little sites with no classes at all!
Obviously this approach has its limits, but it works well for proof-of-concept sites or sites that don't need to be very complex or dynamic. Just a sensible font size, nicer looking form elements, etc.
It's a CSS stylesheet you include in every page/view. You don't add any classes to your HTML and rely on the defaults of that stylesheet to style the semantic markup. If those defaults are good for your project, and you have some command of HTML elements beyond using divs and spans for everything, it saves a lot of time.
Obviously this approach has its limits, but it works well for proof-of-concept sites or sites that don't need to be very complex or dynamic. Just a sensible font size, nicer looking form elements, etc.
Here is a list of classless CSS frameworks: https://github.com/dbohdan/classless-css