The header should not be part of the tbody as in
Have a look here HTML tbody tag
98% of browser problems are caused by code errors in your page. Fix reported code errors. And do this often during development to ensure your code is clean and cross browser friendly.
While the error was in a css rule that I thought that I deleted, the W3C Markup Validator is a great tool, and it will be extremely useful.
A big problem (as I stated to Ben as well) is that I have a hard time using Dreamweaver to apply css rules. Oftentimes what I think I have selected isn't, and sometimes the highlighted css area changes unexpectedly in the midst of editing. Do you have any advice?
I also want to thank you for your multiple replies on this forum. While I was lurking trying to find an answer, your replies were often very helpful for other issues (like cleaning up my contact form). Thank you!
The W3school.com website left me feeling like a kid in a candy store, although I realize my coding is like a bull in a china shop. Many useful toys and tools.
I cleaned up my table tags (and correctly labeled the 'scope' as well), but the problem persisted. It turned out to be a css rule that I thought that I had deleted. I have had a hard time using the Dreamweaver visual selection and designer area (the highlighted css rule seems to move on its own). Perhaps learning to hand code css rules would be most appropriate.
Thank you so much in making this forum a useful place. I appreciate the time and effort that you have made!