Checky is a Mozilla plugin for checking a page with a variety of validators and services. You can check using just one service, or configure the agent to use several at once. Validate your XHTML, CSS, and RSS, and check accessibility through one convenient interface. I love this thing.

These are the browser-based web development tools I now use on a daily basis:

All but ViewStyles are Mozilla-based. If you’re a web developer and are not using Mozilla, you’re missing out.

Of course, I’d also like to know what I’m missing. Dangit, I really need to set up comments.