Since no one answered this, I did a little experimenting and here is what I found:
- When a solution is opened and the default layout has a slider control with a web viewer control on one of the hidden slides, the user can't do anything until the web page loads (or it generates a file not found error).
- If I set up the web viewer the way that I want it -- except for the URL -- the solution loads much faster.
- If I dispense with the navigation dots for the slider control and give the user buttons, I can use a Set Web Browser step in the button that goes to the web viewer slide. I specify the URL in the script step.
- The first time a user navigates to the slide that contains the web viewer it is as slow as it would have been if it loaded on startup. If the same, fixed URL is going to be used for every record (in this case it's a help page on a web site), the page doesn't need to load again. It is available instantly every time the user navigates to the slide.
So the answer is, you can force a web viewer control to load a page when you want it to load and it's probably not best to do it at startup unless you're sure it's always going to be there and the users won't mind the wait.