To perform server side validation we have an event 
called ?ServerValidate?. 
Syntax:
ValidationControlName_ServerValidate(s, args)
{
?..//Logic
}

It's simple use server validation control.Just drag 
validation control which u required. then set property as 
like controlTovalidate,Set proper message. Finally set 
value of validation.it depends on which validation control 
using if u use 1.Requiredfiledvalidation-then set initial 
value
2.Range validator-Max value and min value
3.Regularexpressionvalidation-use format email,phone etc.
4.Compaire validation-Two controls contol of compare and 
its operator -less,greater,Equal etc.
5.Custom validator-U can call ur javascript function.
6.Summary validation-is' showing summary of all validations