Set up one computer with your presenter's view and another logged on as an audience member. This gives you a much better sense of what your participants are actually experiencing. Slides that are slow to advance for you may display quickly for the audience. This will also allow you to check the formatting and apperances of your visuals from the participant's perspective. Finally, don't go looking for trouble .
Glitches can happen during any type of presentation whether in person or over the Web.
In web-based events, glitches are often only an issue if they are acknowledged by the presenter. Just make a mental note to advance slides a little sooner and no one will be the wiser.