If you look at the above URL, the paragraph should have a double, think border set with this stylesheet: border-style: double; border-width: thin; the border does not appear with the latest "nightly" build on a linux system. It does however seem to work with Netscape 4.7. If I try other values for border-width, the border will appear correctly as a double style. If I try other styles with thin width, everything will be ok. It seems to be just this combination.
According to the spec, the sum of the two lines and the space between them must equal the value of 'border-width'. Since you set the border width to 'thin' which is 1 pixel, we get 1/3rd of a pixel for each line and the space between so nothing gets displayed. When using a 'double' border, you should set the width to a minimum of 3px or 'medium'.
Reopening to mark duplicate. We should be handling this case better.
*** This bug has been marked as a duplicate of 1781 ***