To Focus on First column of first row in gridview firstly we have to get the id of the textbox where we have to focus and call a inbuilt focus method.
$(document).ready(function () {
sys.WebForms.PageRequestManager.getInstance().add_pageLoaded(fcs);
fcs();
});
function fcs() {
document.getElementById('ctl00_ContentPlaceHolder1_grid_inv_ctl02_name').focus();
}