//Checking for Characters only (without spaces)
function charactersOnly(fieldName)
{
	var validChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_";
	var temp;

	for(var i=0; i < fieldName.length; i++)
	{
		temp = fieldName.substring(i,i+1);
		if(validChars.indexOf(temp) == "-1")
		{
			return false;
		}
	}	
}
  function validlogin(form){
   var field0 = form.username;
   var field1 = form.password;
//username length
   if (field0.value.length < 3) {
      alert("Please recheck your username, it appears to be invalid");
      field0.focus();
      field0.select();
      return false;
   }
//username no invalid chars
   if (charactersOnly(field0.value) == false) {
      alert("Your username cannot contain spaces or invalid characters");
      field0.focus();
      field0.select();
      return false;
   }
//password length
   if (field1.value.length < 3) {
      alert("Please recheck your password, it appears to be invalid");
      field1.focus();
      field1.select();
      return false;
   }
}