Everything about how ASP.NET works, how you can secure things, how you can impersonate, how IIS6 so much owns IIS5 ;)
Some of the things I learned here was that you can have a web.config per directory. I always thought it was one per app.
Also, that you should not forget to set debug="false" when going to production. Something I've been guilty of already, easy to forget.
Some nice options to recycle the ASP.NET worker process as well, like each week, each 1million request, memory limit, etc
Multiple worker processes.
How an upgraded dll get's taken care off. Overwrite it, old clients still use the old dll, which is in cache, and new visitors get the new one, untill all old visitors are timed out and the old dll is completely gone.
How 'eif' (need to get the url from the slide, it got updated, will try tomorrow) is very usefull for developers to easily log to the event log.
Some nice options with Trace="true", which gives you a complete overview of what your page does. This dus make some debugging easier!
Also when you got Trace enabled site-wide that the trace.axd has a trace per request.
I'll be checking those tracing options out for sure, very nice.
Last session also covers ASP.NET, so I'll add it here. It's the Overview of ASP.NET Whidbey.
First of all, I hate the MS logos in this room, those which keep spinnging around and around in the room and straight into your eyes every X seconds.
There were 2 speakers (got to check their names later on), which were a comic duo I thought. They keep running around, they made a very good impression, and one of them spoke English with a very Dutch accent, it amuzed me to hear some pieces in english and others pronounced in typically dutch. (Note: this is not a negative sentence :p)
I'm sure you all saw what nice Whidbey has to offer, I love the built in webserver. This will finally allow me to easily debug. Even when not having Admin rights.
They gave a lot of demo's about Master Pages, Authentication, User Management, DataAcces 'Things' (forgot the name, remember everything comes from System.Thing. But in the end they also had too little time, seems like everyone had :)
This was the last session of the day, after that was the closing keynote and the Geek Fest, with plenty of food.
On to day 2 :)
Hope you all enjoyed this feedback from me.