I would like to create a one page website, and split the screen into 100 squares, filling the page...
How can this be done other than creating a table?
There are too many ways of creating such a layout to try to make any relevant suggestions without knowing more about what you're trying to do. If you'll be more specific about your ideas, you'll get some answers.
If you just want a page with 100 images, you could use the free JAlbum software which also writes the code for you. All you need is a Skin to use that you like and set the options/preferences. Couldn't be easier.
Maybe you could float the images and set the width on 1%.
Something like this:
<img src="picture1.jpg" class="picture" alt="picture" />
<img src="picture2.jpg" class="picture" alt="picture" />
<img src="picture100.jpg" class="picture" alt="picture" />