Help，problem of the listheader’s align attr on ie6

<window id="rw" title="Embedded Style" border="normal" width="600px">
				<listbox >
					<listhead>
						<listheader label="123" sort="auto" sclass="blue" align="center" />
						<listheader label="234" sort="auto" sclass="blue"/>
					</listhead>
					<listitem>
						<listcell label="aaaa" />
						<listcell label="aaaa" />
					</listitem>
					<listitem>
						<listcell label="cccc" />
						<listcell label="vvvvv" />
					</listitem>
				</listbox>
		</window>