jQuery.fn.selectItem = function(targetId) {
var _seft = this;
var targetId = $(targetId);
this.toggle(
function() {
var A_top = $(this).offset().top + $(this).outerHeight(true); // 1
var A_left = $(this).offset().left;
targetId.bgiframe();
targetId.show().css({ "position": "absolute", "top": A_top + "px", "left": A_left + "px" });
}
, function() {
targetId.hide();
}
);
targetId.find("#selectItemClose").click(function() {
targetId.hide();
});
targetId.find("#selectSub :checkbox").click(function() {
targetId.find(":checkbox").attr("checked", false);
$(this).attr("checked", true);
_seft.val($(this).val());
targetId.hide();
});
$(document).click(function(event) {
if (event.target.id != _seft.selector.substring(1)) {
targetId.hide();
}
});
targetId.click(function(e) {
e.stopPropagation();
});
return this;
}

<input type="text" id="txtCompetencies" value="All" readonly="readonly"/>
<div id="selectCompetencies">
<table>
<tbody>
<tr><td><input type="checkbox" />All</td></tr>
<tr><td><input type="checkbox" />Confidence</td></tr>
</tbody>
</table>
</div>

/* pop div begin */
.selectItemcont{padding:8px;}
.selectItemtit{line-height:20px;height:20px;margin:1px;padding-left:12px;}
.bgc_ccc{background:#E88E22;}
.selectItemleft{float:left;margin:0px;padding:0px;font-size:12px;font-weight:bold;color:#fff;}
.selectItemright{float:right;cursor:pointer;color:#fff;}
.selectItemcls{clear:both;font-size:0px;height:0px;overflow:hidden;}
.selectItemhidden{display:none;}
#selectCompetencies
{
display:none;
background:#FFF;
position:absolute;
top:0px;
left:center;
border:1px solid #000;
overflow-x:hidden;
overflow-y:auto;
width:250px;
z-index:1000;
max-height:200px;
}
/* pop div end */

$("#txtCompetencies").selectItem("#selectCompetencies");