function isDiggit(c) {
	var test = "" + c ;   
	if ( test=="0" ||  test=="1" ||  test=="2" ||  test=="3" ||  test=="4" ||  test=="5" ||  test=="6" ||  test=="7" ||  test=="8" ||  test=="9") return true;
	return false; 
}

function hasPermittedLetters(s) {
	var sn=s.length;
	for (var k=0;k<sn;k++) 
	  if(!isDiggit(s.substring(k,k+1))) return false;
	return true;
}

function v() {
	if (!document.f.Your_name.value) {
	  window.alert("Your name must be filled in!");
	  document.f.Your_name.select();
	  document.f.Your_name.focus(); return false; } 

	if (!document.f.Phone_Number.value) {
	  window.alert("Phone number must be filled in!");
	  document.f.Phone_Number.select();
	  document.f.Phone_Number.focus(); return false; } 
	else {
	  p = document.f.Phone_Number.value; 
	  if(p.length < 8) {  
	    window.alert("Sorry, the phone number format you entered is wrong!");
	    document.f.Phone_Number.select();
	    document.f.Phone_Number.focus(); return false; 
	  }	  
	  if(!hasPermittedLetters(p)) {  
	    window.alert("Sorry, the phone number can contain only diggits!");
	    document.f.Phone_Number.select();
	    document.f.Phone_Number.focus(); return false; 
	  }	  

	}
	  
	return true;
}