Helpful online tools

These are a bunch of online tools which I find indispensable when I need to do some quick validation, encoding, or formatting/indenting.

1. XML escaping - http://escapehtmlforxml.com/
   
2. XML indenting (critical when trying to read ugly XML) - http://xmlindent.com/
3. JSlint (javascript code checker) - http://www.jslint.com/
4. JSONlint (JSON validator and formatter) - http://www.jsonlint.com/
5. W3C HTML validator - http://validator.w3.org/
6. W3C CSS validator - http://jigsaw.w3.org/css-validator/
7. WDG tools (web validators) - http://htmlhelp.com/tools/
8. XHTML/CSS page validator - http://xhtml-css.com/
9. shell tools (xml, base64, md5/sha1, and more) - http://www.shell-tools.net/

Hope this list of tools is helpful!

Validating CSS online

I recently had a problem with a webapp where things were showing up but I could not figure out why. The CSS seemed correct at a glance but someone else had written it so I was not very familiar with it. After struggling for awhile I did the smart thing and asked Gonzalo Silverio if he had any ideas (which of course, he did). He pointed me to this awesome CSS validator at http://jigsaw.w3.org/css-validator/. You can upload a css file or simply provide a URL to the file and it will give you a nice little report that tells you what is wrong.
A similar service for validating your markup is available at http://validator.w3.org/.