function advance(currentField,nextField) {
    if (currentField.value.length == 4)
        document.login[nextField].focus();
}
function validate()
{
	  // checking whether all the fields are empty
	   if (document.login.T1.value==""){
	   if (document.login.T2.value==""){
	   if (document.login.T3.value==""){
   
		alert("Please enter either your Email ID or Membership ID");
		document.login.T1.focus();
		return false;
  }
  }
   }
   // validatin empty
    if (document.login.T1.value!=""){
	if (document.login.T2.value==""){
	alert("Invalid Membership ID! ");
		document.login.T1.focus();
		document.login.T1.value==""
		return false;
  
  }
   if (document.login.T1.value.length < 4 )
   {	 
   alert("Invalid Membership ID! ");
		document.login.T1.focus();
		document.login.T1.value==""
		return false;
  
  }	} 
 
   if (document.login.T2.value!=""){
   if (document.login.T1.value==""){
   alert("Invalid Membership ID! ");
		document.login.T2.focus();
		return false;
  
  }
  if (document.login.T2.value.length < 4 )
   {	 alert("Invalid Membership ID! ");
		document.login.T2.focus();
		return false;
  
  }	   
  }
  
   
   //checking  character entry
   		var count=0
		var val = document.login.T1.value
        var len=val.length

       for(var counter=0;counter<val.length;counter++)
	    {
		    charascii=val.charCodeAt(counter)
	  	     if(!((charascii > 47 && charascii < 58)))
		      {
		        count++
		      }
		     
	     }   
     
        if (count > 0)
         {
           alert ("Invalid Membership ID!!!")
           document.login.T1.value=""
		   document.login.T2.value=""
			 document.login.T1.focus()

           return false
         }  
         
		var val1 = document.login.T2.value
        var len=val1.length
        
	    for(var counter=0;counter<val1.length;counter++)
	    {
		    charascii=val1.charCodeAt(counter)
	  	     if(!((charascii > 47 && charascii < 58)))
		      {
		        count++
		      }
		     
	     }   
     
        if (count > 0)
         {
           alert ("Invalid Membership ID!!!")
		   document.login.T1.value=""
           document.login.T2.value=""
			 document.login.T1.focus()
           return false
         }
		 
	/* var val2 = document.login.T2.value
		 if (val2.length < 4 )
		 {
           alert ("Invalid Member ID!!!")
           document.login.T2.value=""
			 document.login.T2.focus()
           return false
         }*/
		 
//checking email valid or not
	
     if (document.login.T3.value!=""){
   
    emailStr=document.login.T3.value;
	var emailPat=/^(.+)@(.+)$/
	var specialChars="\\(\\)<>@,;:\\\\\\\"\\.\\[\\]"
	var validChars="\[^\\s" + specialChars + "\]"
	var quotedUser="(\"[^\"]*\")"
	var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/
	var atom=validChars + '+'
	var word="(" + atom + "|" + quotedUser + ")"
	var userPat=new RegExp("^" + word + "(\\." + word + ")*$")
	var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$")
	var matchArray=emailStr.match(emailPat)
	if (matchArray==null) 
	{
		alert("Please enter a valid Email Id");
		document.login.T3.focus();
		return false
	}
	var user=matchArray[1]
	var domain=matchArray[2]
	if (user.match(userPat)==null) 
	{
	    // user is not valid
	    alert("Email Id cannot have 2 @ symbols");
		document.login.T3.focus();
	    return false
	}
	var IPArray=domain.match(ipDomainPat)
	if (IPArray!=null)
	{
	  for (var i=1;i<=4;i++) 
	  {
	    if (IPArray[i]>255) 
	    {
		   alert("Domain Name cannot be less than 3 characters");
		   document.login.T3.focus();
		   return false;
		}
	  }
	    return true
	}
	var domainArray=domain.match(domainPat)
	if (domainArray==null) 
	{
		alert("Check the email Id after @ symbol. Enter a valid Email ID");
		document.login.T3.focus();
		return false
	}
	var atomPat=new RegExp(atom,"g")
	var domArr=domain.match(atomPat)
	var len=domArr.length
	if (domArr[domArr.length-1].length<2 ||  domArr[domArr.length-1].length>3) 
	{
	   alert("Email Id extension cannot be less than 2 or greater than 3 characters");
	   document.login.T3.focus();
	   return false
	}
	if (len<2)
	{
	   alert("Please enter a valid extension for the Email Id");
	   document.login.T3.focus();
	   return false
	}
	}
	
	
	}