When we go for shopping online, we purchase any item say CD, Books and place order. To ship our order company ask for our billing as well as shipping address. If we going to gift that item to anyone then both addresses will be different else will same. For same billing and shipping address shopping cart gives us an option. By clicking (checking/selecting) it our billing address content get fill in shipping address field which save our time to retype same address again. All the process of auto filling data is done by JavaScript. Here we are going to design JavaScript Auto filling data for ASP.NET web forms. Also we are going to lock those fields as we simply coping data from one data field to other.