Carefully compared to a lecture in an auditorium, a web conference is only somewhat different. The audience can't see you, but they can hear you very well. And much like an auditorium, you can have documents, graphs, and video placed in front of the audience's eyes with perfect timing. The content of your presentations—both in a web conference and an auditorium--can be greatly enhanced by visuals, but what if your visuals are subpar? Will your presentation be greatly affected?
According to Dave Paradi, poor visuals can only lessen the impact of an auditorium presentation. Paradi's example entailed a lecture by an esteemed academic and expert in his field. While the studies and conclusions were well researched and told to the audience clearly, the visuals were poor and not used very effectively. However, Paradi says that the content of the presentation was well received by the audience anyway.
Paradi's conclusion is that "great content will trump poor visuals." The audience will leave informed and enlightened, but not to the extent they could have been. For a lecture in an auditorium, I agree with Paradi. When you stand in front of an audience, you are the presentation, not your visuals. Your words—and body language—can only be enhanced by pictures, video, and such.
For a web conference presentation, I disagree completely; great content can be sunk by poor visuals. After all, in a web conference there is only your voice and visuals to drive the presentation. If the graphs are confusing, the pictures blurry, and the documents not spell-checked, the participants can be greatly distracted from what you're saying.
However, I do like Paradi's solution, and it's even more effective for web conferences: create the presentation and the visuals separately. Don't fire up PowerPoint and use it to create your outline and main points. Don't look for pictures to talk about.
Leave all but a blank page to write your presentation, and only afterwards find great visuals to enhance the content of your web conferences.