Several years ago I was involved in developing a Web app server that allowed the apps to be written in one language, HTML/XHTML/XML with a few extensions. I had been working with PHP and had reached the point where dealing with two languages intermixed (HTML and a C-like programming language) was a pain and was running out of steam. Just one language had a lot of appeal. After a lot of work by several people, we decided that maybe one language was a great idea, but this wasn’t the one.
I am now working with Ruby on Rails. It is several languages, Ruby, HTML/XHTML, and possibly Javascript (for AJAX). It is fun, but I noticed that I write only the simplest bits of HTML. The fancier bits are generated by Ruby code. And I am not writing any Javascript, just Ruby code that generates the Javascript. It’s getting closer to one language, and not the one I expected.