This. Is. Brilliant.via ajaxian:

Steve Souders, performance architect at Yahoo!, announced today the public release of YSlow.

Stoyan Stefanov reviewed it briefly and gave tips for custom scoring at his blog.

What’s YSlow?

It’s an extension to Firebug (yes, correct, Firebug, not Firefox) that helps with performance optimization efforts. It scores your page on the scale A to F, based on compliance with Yahoo’s performance rules. It’s a tool that has been used internally at Yahoo and is now released to the world.

Steve is going to be speaking about YSlow at the Ajax Experience that just kicked off. I am looking forward to meeting him and check out the tool. We should give it a run on your sites and post how you did (don’t run it on Ajaxian ;).

Hi gang,

Been out of town for a week and now that I’m back it’s time to smash a few bugs:

• Fx.SmoothShow – refactored the exploration of the element dimensions when hidden so that it isn’t visible to the user (you won’t see items “flicker” before the show transition anymore)
• element.position – refactored to allow for more than just the previous 5 positions, now supports nine: all corners, all mid-points between those corners, and the center (examples)
• string.cnet.js – fixed up the query string logic to url-decode values
• element.legacy.js – added Element.setText for users who aren’t up to Mootools 1.0
• date.picker.js, product.picker.js, stickyWin.default.layout.js, stickyWin.js – now all use Element.setText for css injection (fixes IE6 probs)
• dramatic refactor of tabswapper; now tabs can be added, removed, moved. Additionally, you can now pass in for tabs, sections, and clickers a dom collection or a selector.