Server Side Validation in Web Apps

I took a long break and now back again with Active blogging. Its good to be back.
This time I am discussing the importance of server side validation. I observed many of merchant's sites has a client side validation usually using JavaScripts , after validating the data like if the Integer's value is within some bounds ,it does not get validated again on server which can cause a huge error while making transactions on the server , As Javascript validation can be manupulated any time on the client, here is link which shows how easy it is to modify the validation using Javascript. Without validating data again on server and processing it can break the system easily. Java script validation should only be used to avoid round trip to the server nothing beyond that and data should again be validated on the server.