How to open jQuery Popup?

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Javascript

HTML

I want open Popup on click image. i am using this code...

<script language="javascript" type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript">

$(document).ready(function ()
{
$("#btnShowSimple").click(function (e)
{
ShowDialog(false);
e.preventDefault();
});

$("#btnShowModal").click(function (e)
{
ShowDialog(true);
e.preventDefault();
});

$("#fancybox-close").click(function (e)
{
HideDialog();
e.preventDefault();
});

$("#btnSubmit").click(function (e)
{
var brand = $("#brands input:radio:checked").val();
$("#output").html("Your favorite mobile brand: " + brand);
HideDialog();
e.preventDefault();
});

});

function ShowDialog(modal)
{
$("#overlay").show();
$("#dialog").fadeIn(300);

if (modal)
{
$("#overlay").unbind("click");
}
else
{
$("#overlay").click(function (e)
{
HideDialog();
});
}
}

function HideDialog()
{
$("#overlay").hide();
$("#dialog").fadeOut(300);
}


</script>

and Style Sheet also in Head section