How to use customize a data view to to have a URL to poup a new window.

I created a link List below WSSv3 and i want the link URL to poup a new
window.
If i add target=_blank to the href anchor section below and save it.
It works but when i try to modify the view from sharepoint i can't get to
modify anything the view shows half of the normal page options
and all my other nice setting like shaded box sorting/filtering  on the page
stops working.
Any ideas what i'm doing worng?

select="substring-after(@URL, ', ')" /></xsl:when>
SRC="{substring-before(@URL, ', ')}" ALT="{substring-after(@URL, ', ')}"
/></xsl:when>
HREF="{substring-before(@URL, ', ')}">
disable-output-escaping="no" select="substring-before(@URL, ', ')"
/></xsl:when>
')" /></xsl:otherwise>