Compare this page:

http://www.gocmo.com/index.shtml

With this one:

http://www.gocmo.com/faq.shtml

You'll notice that in the first one, there is no black line on the
right side, while the second one has a black line on the right side. 
They are both supposed to have a black line on the right side.

Any idea what's going on?

wizardofyendor-ga:

Well, it took longer to track down than I thought it would, but I
found the culprit for you.

The reason why the right border disappears is because of the use of
the <em> tag in the contents. This causes the browser to use the
default emphasis type, italics, for the included text. However,
italics fonts tend to be, well, inaccurate, so when the browser
calculates the table width, it calculates it using what it thinks is
the right width, but when it displays, the italics causes it to use up
one more pixel than it should, causing your border to disappear on the
right.

There are two easy ways to fix this. One is to not use the <em> tags.
The other is to reduce the specified width of the lowest-level table
from 100%, to 99.9%. Now, Internet Explorer supports the use of
decimal percentages in specifying table widths, your results may vary
on other browsers. However, if you absolutely must use the <em> tags,
then reducing the width is your next best option.

Regards,

aht-ga
Google Answers Researcher

Thanks.  Problem solved, as you can see from my website.  I wouldn't
have figured that out in a million years.