Applying this HTC to a <td> table cell results in all styles (including borders) on the <td> cell being removed.

Applying it to a <table> gives a correctly rounded border, but the whole table turns solid black, obscuring the table contents.

Applying it to a <tr> table row appears to have no effect at all.

Tr wont have effect as it is not having displayable body part. Appliying to TD is being mess because it reproduces VML tags in ie. You can change backgound colour applied on table . By default it is black