<xsl:value-of select="Top"/> will select the textual value of the <Top> element. I'm guessing you actually want to ouput the string 'Top' instead.
Try <xsl:value-of select="'Top'"/>.
Better still, get rid of the <xsl:element> and <xsl:attribute> instructions and do it like this:
Code:
<TD valign="Top" width="{../../../@colwidth}%">
... blah blah blah
</TD>