树形列表不展开问题

如图

代码1：
<script>
function ExpandCollapse( el )
{
var tr = el.parentElement.parentElement;
var tbl = tr.parentElement.parentElement;
var sDisplay = ( el.src.indexOf( "minus" ) == -1 ) ? "" : "none";
var sDisplayReverse = ( el.src.indexOf( "minus" ) == -1 ) ? "none" : "";
el.src = "../ags/images/expand_" + ( el.src.indexOf( "minus" ) == -1 ? "minus" : "plus" ) + ".gif";
for ( var i = tr.rowIndex + 1; i < tbl.rows.length; i++ )
{
var trCurrent = tbl.rows( i );
if ( trCurrent.cells( 0 ).firstChild && trCurrent.cells( 0 ).getElementsByTagName( "IMG" ).length )
{
if ( tr.cells(0).style.paddingLeft =="" && trCurrent.cells(0).style.paddingLeft =="20px" )
{
if (el.src.indexOf( "minus" ) == -1 )
{
trCurrent.cells(0).getElementsByTagName("IMG").item(0).src = "../ags/images/expand_plus.gif";
}
}
else {
break;
}
}
if ( tr.cells(0).style.paddingLeft =="" && trCurrent.cells(0).style.paddingLeft =="40px" && el.src.indexOf( "minus" ) >0 )
{
trCurrent.style.display = sDisplayReverse;
}
else {
trCurrent.style.display = sDisplay;
}

}
}
function StartHidden(el)
{
var tbl=el.parentElement.parentElement.parentElement.parentElement;
for (var i = 0; i < tbl.rows.length; i++)
{
var trCurrent = tbl.rows(i);
if (trCurrent.cells(0).style.paddingLeft.indexOf("px") > -1)
{
trCurrent.style.display = "none";
}
}
}
</script>


代码2：
'<img onclick=''ExpandCollapse(this)'' src='../ags/images/expand_plus.gif' style=''cursor:hand; vertical-align:middle; margin-right:2px''/>
<span onclick=''ExpandCollapse(this.previousSibling)'' style=''cursor:hand''>'+..+'</span>'



代码3：
'<img onclick=''ExpandCollapse(this)'' src='../ags/images/expand_plus.gif' style=''cursor:hand; vertical-align:middle; margin-right:2px''/>
<span onclick=''ExpandCollapse(this.previousSibling)'' style=''cursor:hand''>'+..+ '</span>'


代码4：
<img src='../ags/images/expand_plus.gif'/>



显示如下：



如图写在JS中的字段没有展现，而且不能展开。
求解惑。