In simplified terms, one might say that the last rule set counts - so
you'd have to add it to the end of the StyleSheet tiddler* if there are
other definitions for tables above.
If that doesn't work, try increasing specificity by adding the viewer
class in front of each selector:
.viewer table,
.viewer table tbody,
.viewer table tr,
.viewer table td,
.viewer table th {
border-left: 0;
border-right: 0;
}
By the way: Since this is an end-user question not related to
development, it should be discussed on the regular [tw] group instead of
here on [twdev]:
http://groups.google.com/group/TiddlyWiki
No worries though, you'll know better next time.
HTH.
-- F.
* please take a look at the note here:
http://www.tiddlywiki.org/wiki/StyleSheet