Hi,
can any one tell,Validation occur server side or client side?why?

Thanks,
Prasath.K

Mainly two type of information that need to be validated
1. Login Credentials (User Info)
2. Data
Credentials
Should be done on server side.
Username and password that will be checked against the data stored in database. So in that case no validation on client side because it is not secure

Data Validation
Should be done on both side
Because client side validation will prompt for specific and mandatory inputs and then server side validation of those data will check that its valid for the your specific purpose or its not malicious.

Client side validation boost up the Performance of the server,Since No Round trip and Less no of Erroneous Data enter into the Server.

The Main disadvantage is It is Insecure. every One can see the Coding using view source and alter and then Submit.

While Server Side Validation is More secure and supports a lot of Langauages