if we need some fields from different tables
temporarily in our software or application then

It's a very common requirement to show hint in textbox when empty
and when textbox gets focus hint goes away.now a days many websites
implemented showing hint.there are many ways to do that by jquery.

when you process credit card payment the two
most sensitive inputs are taken from customer
are card number and card security code.you
will want to verify that the data entered
is valid before processing credit card payment.

when you submit form with input and select
controls,the values of these controls are
passed with form.we get these as POST var-
$_POST["controlname"];

It's a very common requirement to create different types of button and
it's click event handler dynamically in asp.net application.