To change it on the page, right click on design view, and ask for proprties. It's in there in a list box (Grid & Flow).
To change it on a project, right click on the project, ask for properties, select designer defaults on the left, and again, it's in a list box.
To change it forever, you can modify the templates, which you can find on your computer at:
C:\Program Files\Microsoft Visual Studio .NET\Vb7\VBWizards\WebForm\Templates\1033
Note the vb7 there... each language has it's own templates. Actually, this is where you can create your own boiler plate projects, as well as monkeying w/ the existing ones. You'll notice that there's a folder for each of the options you see in VS. Add a folder and templates, and you're adding to the options you'll see.

paul