When you're learning HTML and CSS, how do you try out examples? Do you use a less-advanced freeware tool, or do you set up a full-blown Integrated Development Environment (IDE) like Eclipse or Visual Web Designer Express?
Sometimes, it's just not convenient to use a "real" tool - maybe you're away from your development computer, or you just want to check out a couple of CSS commands and would rather not have to load up the full IDE.
And what if you're looking at a web page and are curious about the back-end technology used - is it a Wordpress site in disguise? What back-end server are they using - Apache, Microsoft IIS, or something more obscure? Are they using jQuery, or a lesser-known Javascript library?
Today, Smashing Magazine linked to a couple of articles with tools for Evolving Code Monkeys.
Helpful Tips and Tools For Web Design Experiments, from Design Shack, pitched readers on the Benefits of Experimentation, offered Tips for Experimenting, then got down to business with Tools for Experimenting. There were two free web tools for HTML / CSS and Javascript experimentation.
CSSDesk is an online tool that allows you to work with HTML and CSS, making changes in two windows on the left side of the screen, and watching the results of your changes live in the right hand side of the screen. It's much easier and quicker than opening up a "real" IDE to experiment with a few lines of code.
jsFiddle is more elaborate than CSSDesk, but besides windows to enter HTML and CSS, jsFiddle adds another window to allow you to use Javascript and Javascript libraries like jQuery, Dojo, or YUI. However, the idea is the same - it's a good quick tool to enter a few lines of code and see the result right away.
UnderTheSite.com is a clever online tool that analyzes the technologies used by a website you supply. Just enter the website address, and UnderTheSite connects to the site and detects things like jQuery and other Javascript libraries, Google Analytics, and (sometimes, for some web sites) the type of host server, and the site scripting language or programming framework.
Under The Site is not perfect - for example, analyzing Stack Overflow (the popular techie community answer site) told me that the site is using jQuery, Backbone.js, Google Analytics, and the Google Libraries API. However, I wasn't able to find out whether Stack Overflow is using Microsoft's C# language or an Open Source language like PHP or Ruby. I even got a "500 Server Error" page when I queried Under The Site for my employer's home page. However, when Under The Site does work, it's a quick, easy way to peek behind the curtain.