JQuery can't find my div element

JQuery can't find my div element

I have jquery function in my script file:
function modalpopup(id)
{
var searchid = "\"#" + id + "\"";
var element = $(searchid );
element.dialog({
height: 340,
width: 500,
modal: true
});
}
in my asp.net 2.0 file I have the following:
<a id="_ctl0_MainContentPlaceHolder_DataGrid1__ctl2_HyperLinkInfo"
onclick="modalpopup('_ctl0_MainContentPlaceHolder_DataGrid1__ctl2_details10')">
<img src="../Images/info_icon.PNG" border="0" /></a>
<div id="_ctl0_MainContentPlaceHolder_DataGrid1__ctl2_details10"
title="Dialog Title"
style="display: none;">
<center>
<table class="table_class" cellspacing="1" cellpadding="2"
rules="all" border="1"
id="_ctl0_MainContentPlaceHolder" style="border-style: None;
height: 24px; width: 800px;
font-size: 16px;">
<tr class="table_header_class" style="color: DarkGray;
font-weight: bold; font-size: 16px;
white-space: nowrap">
<td style="white-space: nowrap">
customer details </td>
</tr>
</table>
</center>
</div>
Its look like its a simple jquery job to find the div element but the
jquery result is null!!
What I'm doing wrong here? There is no error format in my html code
Please help