>How to write JSP validation routine for HTML form field so that the value is checked on client side.
>Rajesh
Don't know about JSP but if you want client side validation you should use javascript. It does it all and can integrate with a jsp page fairly well.

Alternatively if you are trying to avoid having the page refreshed you can have a hidden frame which is given the data and refreshed as blank with a form and one hidden field. Javascript can read the hidden field and interpret the answer.

example: email field. There are some groovy email validators which "ping" the email address. the hidden frame could have a new page called with the email address given as a parameter. The page comes back with the form saying 'good' or 'bad'. There's an onload javascript function which reads the result and puts an alert up, and moves the focus back to the email field on the visible frame.

It's a bit tricky but could be worth it.

Sarah