[jQuery] edit dialog display issue

Hii..i am new in jqgrid.
i have to achieve following functionality..

I get grid which displays all data..now i want to edit row on
selection changed.
for that i wrote following code as a jqgrid parameters

onSelectRow: function() {
var gr = jQuery("#list").getGridParam('selrow');
if (gr != null) jQuery("#list").editGridRow(gr,
{ reloadAfterSubmit: false, height: 450, drag: true });
else alert("Please Select Row");
}

I have all gridrows with editable:true...
So by that i get the edit dialog , but it displays on middle-top of
the page....

top and left property of editgridrow doen't affect it..

any suggessions????