You can do this:

<kbd>Header 1</kbd><kbd>Header 2</kbd><kbd>Header 3</kbd><br/>
<kbd>Cell 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><kbd>Cell 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><kbd>Cell 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><br/>
<kbd>Cell 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><kbd>Cell 4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><kbd>Cell 5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><br/>
<kbd>Cell 6&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><kbd>Cell 7&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><kbd>Cell 8&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</kbd><br/>

Also:

[tag:Header1][tag:Header2][tag:Header3]<br/>
[tag:Cell-----1][tag:Cell-----2][tag:Cell-----3]<br/>
[tag:Cell-----4][tag:Cell-----5][tag:Cell-----6]<br/>

And the obvious third:

<kbd>[tag:Header1]</kbd><kbd>[tag:Header2]</kbd><kbd>[tag:Header3]</kbd><br/>
<kbd>[tag:Cell-----1]</kbd><kbd>[tag:Cell------2]</kbd><kbd>[tag:Cell-----3]</kbd><br/>
<kbd>[tag:Cell-----4]</kbd><kbd>[tag:Cell------5]</kbd><kbd>[tag:Cell-----6]</kbd><br/>

OK, I'm only serious about the first one. Though if you check the code, you need some nifty `&nbsp;`s :/