Why dont you just make the width smaller? I think that is what most people do. So instead of having your width ="780" now reduce to width="760" or less.
Then play with it. Try different monitors 15,17,19,21 blah blah and try different resolutions you were talking about and different browsers if you want.
Then it doesnt matter who comes along and it can fit into any screen.
100% on the outside table will obviously fill the 1024x768 screen because 100% is very big...actually to big and everything looks small with that resolution. So when a normal person visits your site as 800x600 the 100% table is going to expand the screen and bring up the width scroll bar at the bottom which is very annoying (actually doesnt expand). Unless of course you have a 21+ monitor which it will look fine on but everyone else is SOL.
When you design, Ideally, you want to design with 15 in monitors in mind. However, who is really using a 15 in monitor these days.
There are a few of course.
Good luck.