First off let me say that Sencha is a young company and I am behind their vision 100%. Looks like they're going through some rough waters - their forum has been flooded with spam like I've never seen. Take a look:
In this tutorial I will show you how to reduce your ExtJS4 application load times by half, using Sencha SDK Tools. Also, I will show you how to do a clean custom build, the kind that doesn't cause your production code to occasionally download JS files via autoloader. Another gem of this example - we'll get our "compiled" JS down to just about 100 KB, instead of 500 KB+ that results if you follow other tutorials.
I've come to rely on Sencha's online API for my day-to-day work. Sure, I can use the static docs that come bundled with ExtJS download, but since they introduced API comments, the online version is so much more invaluable.
Unfortunately, today around 8:50 AM PST the docs were down, causing me much grief. Technical difficulties, I guess:
Clean up your act Sencha!