javascript validation for gridview

var theGridView = null;
theGridView = document.getElementById(gridViewCtlId);
for ( var rowCount = 1; rowCount < theGridView.rows.length; rowCount++ )
{
var theGridViewRemarks = theGridView.rows[rowCount].cells[0];
var textbox = theGridView.rows[rowCount].cells[0];
if(isFireFox())
{
var value= textbox .firstChild.nextSibling;
alert(value);
}
else
{
var value= textbox .firstChild;
alert(value)
}
}