Easily Preview the Output of Your HTML and CSS With A Web App
JSFiddle has some options that you can set, such as choosing Mootools or jQuery. It also lets you tidy up the appearance with your code with the click of a button. This doesn’t seem to change your code at all, but can add line breaks and indentations.
When you’re done with your code, you can share a link to it, share it on Facebook or Twitter, or even embed it on a page. That makes JSFiddle not just great for testing out some code, but having someone else take a look at it for you.
Do you have any tools that you use when trying out code?