Regular expression in jquery for validating only alphabetic characters.

You can use jQuery plugins or can create your own logic. For example, on each keyup/keypress check whether user has entered non-alphabetic characters or not. If user has punched non alphabet then return nothing(do not accept as input). 
$(function(){
 $('input [id$=txtAlphabetic]").keyup( function(e){
         if( this.value.match(/[^a-zA-Z0-9]/g) )
        {
        //return false; OR replace entered char with nothing but ''. it is upto you.
        e.preventDefault();
        }
 });
});


If you are using jQuery.validate then add your own function to jQuery. Refer: http://stackoverflow.com/questions/5155492/jquery-validation-for-alphabets