Stack Exchange network consists of 177 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Software Engineering Stack Exchange is a question and answer site for professionals, academics, and students working within the systems development life cycle. It only takes a minute to sign up.
Is there any existing in-use, or even just conceptual attempts at creating a markup or programmatic expressions for designing the layouts of websites other than HTML/CSS?
If there are others out there and they do not appear to be in heavy use. Why is this?
Moderator note: this is intended to be a canonical list; please check to see if your suggestion has already been added to the answer. If it hasn't, edit the answer to add yours preferably with an explanation or reason why you're suggesting it.
HAML and SASS are not alternatives to HTML. They are server-side languages that create HTML output. AXR is an alternative to HTML in the making. The AXR site says if you want to help out you can http://axr.vg. GRML is also an alternative to HTML, although I am not advocating to use it or not to use it. I am merely stating a fact. It hasn't been updated in 8 years and doesn't support any browsers but it's own. http://www.codeproject.com/Articles/3486/An-alternative-to-HTML-and-current-web-browsers