Let me take a minute to esplain something. A browser has to interpret the instructions you give it the best way it can. If something has not been specified one way or another, most browsers will try to come up with an attractive solution. The best thing you can do as an author is to specify as much as you can, especially those things that are important for your page to look right. It is also important to view your work through those browsers that people actually use. Since most people use Netscape or Internet Explorer, that is a good start. You may also want to have a copy of a couple other less popular browsers to be sure that you look right to them too.
Another consideration is screen resolution. I work on a 640x480 screen. Many people use 800x600 and many have theirs set to 1024x768 or even 1600x1200. This simple difference has the potential to seriously mess with your page design. There is a little Win95 utility that I use called QuickRes that can change your screen resolution back and forth with the click of a button. It's not a bad idea to view your pages through other resolutions.
Now we will play with COLSPAN (Column Span) and ROWSPAN (Row Span maybe??). Let's suppose Ed beats the crap out of Tom and throws him out of the table. Just doing that, this is what we have.
<TABLE BORDER=3> <TR> <TD>Ed</TD> <TD>Rick</TD> </TR> <TR> <TD>Larry</TD> <TD>Curly</TD> <TD>Moe</TD> </TR> </TABLE>
It just left an empty spot and Rick slid over to fill the void.
<TABLE BORDER=3> <TR> <TD COLSPAN=2>Ed</TD> <TD>Rick</TD> </TR> <TR> <TD>Larry</TD> <TD>Curly</TD> <TD>Moe</TD> </TR> </TABLE>
To emphasize the point I made earlier, about the browser trying to find an attractive solution, let's make Ed span two columns but we'll put Tom back in. We will deliberately introduce a discrepancy just to see how the browser handles it.
<TABLE BORDER=3> <TR> <TD COLSPAN=2>Ed</TD> <TD>Tom</TD> <TD>Rick</TD> </TR> <TR> <TD>Larry</TD> <TD>Curly</TD> <TD>Moe</TD> </TR> </TABLE>
The point is 1) The browser is very forgiving in that it does the best it can with what you give it. 2) It is very important to specify what is important and make sure there are no discrepancies or you may end up with a surprise. And 3) there's very little you do with html will crash the other person's browser no matter how badly you may have messed it up, so don't worry about that.