[Interrobang]

I'm trying to create a table using HTML as well as some CSS, and I've run into two problems.

First, I've noticed that when I define a color for the lines in between the table cells, it actually makes them two different colors, one of which is your specified color and the other is another color which goes well with the first. In tables, this is pretty unnoticeable and makes it look nicer, in my opinion. However, the computer seems to always decide the second color by itself; is there any way to specifically define both colors?

Also, when I open my code with Chrome or Safari, it appears to work fine; however, all the cell lines are missing with both Firefox and Opera (having a Mac, I can't test IE). What could be causing this? I know this is the type of problem in which I'd most likely have to post all of my code for it to be resolved, but since this is a school assignment, that'd be going against forum rules. Any advice as to what might be causing this problem?

If you can think of anything that might solve either question, please let me know. Thanks in advance!