DEMOfall 2010 is a one shot deal
If you are presenting on the stage at DEMO, you have probably realized that it's a one shot deal. Once Matt Marshall introduces you and the music and applause subsides, the clock starts at 6 minutes and the cameras are filming. There is no stopping or retakes. It is literally a one shot deal. In order to make sure that you are prepared for anything and everything on stage, it is reeeeeeeeeeeeeeeally important that you have a back up plan, in case something doesn't go according to plan. If you don't have a back up plan, it can be a very stressful and disappointing 6 minutes for you, your company and the audience. I have seen people back stage in tears because the demo went the wrong way and failed. And, it's usually because they didn't have a back up plan.
There are many things you can do to prepare for the unexpected. One way, if you have a laptop involved in the demo, is to take screen captures of all of the screens you'll need to show using something like SnagIt. It not only allows you to capture the entire scrolling screen, it actually will capture some of the functions too, such as basic HTML. This way, your back up screens will have some basic functionality to show such as drop down lists and Alt Text. You can put all of the files on a USB drive and have instant access to them, if something goes wrong with your product.
Finally, having a back up plan is not enough. You need to practice the back up plan too! If you make time to practice the back up plan, you'll be more likely to succeed on stage, if you need to resort to it. One of the best things to do is during each practice session, run the back up once. The more comfortable you are with it, the easier it will be to handle a mishap on stage. And, if you are paranoid like me, you'll have 2-3 back up plans, depending on what you are doing.