Haml is an alternative syntax for HTML that has gained a large amount of traction in the Ruby community. Though not to everybody's taste, Haml is (primarily due to support for other markup languages) an ideal language for writing rich pages in Nesta.
The Haml web site explains the rationale behind Haml as:
Haml is based on one primary principle. Markup should be beautiful.
Now, I mentioned earlier that Haml is a superb markup language for creating complicated pages with plenty of content in Nesta. Why? Well, on occassion you will want to apply HTML classes to images or write custom markup, in the middle of a page. Haml allows you the full power of HTML, without all the funny brackets.
Have a look at the source of this page for an example.
I wrote the previous few paragraphs in Markdown, and this one in