function checkEmailFormat ( Emaill1 )
{
   var len = Emaill1.length;
   var ck =0;
   if(len==0)
      return(-1);
   for(var i=0;i<len;i++)
   {  var c= Emaill1.charAt(i);
      if(!((c>="A"&&c<="Z")||(c>="a"&&c<="z")||(c>="0"&&c<="9")||(c=="-")||(c=="_")||(c==".")||(c=="@")))
         return (-3);
   }
   if((Emaill1.indexOf("@")==-1)||(Emaill1.indexOf("@")==0)||(Emaill1.indexOf("@")==(len-1)))
      return(-4);
   if((Emaill1.indexOf("@")!=-1)&&(Emaill1.substring(Emaill1.indexOf("@")+1,len).indexOf("@")!=-1))
      return(-4);
   if((Emaill1.indexOf(".")==-1)||(Emaill1.indexOf(".")==0)||(Emaill1.lastIndexOf(".")==(len-1)))
      return(-5);
   return (0);
}


function check_mail( Emaill1 )
{  if (Emaill1!=''){
   var ck= checkEmailFormat(Emaill1);

   if(ck==-1)
   {
      alert("\n\n You have to provide your E-mail address.");
      return false;
   }
   else if(ck==-3)
   {
      alert("\n\n The E-mail address should \n contain only English characters, \n '-', or '_'. Other characters cannot be used.");
      return false;
   }
   else if (ck==-4)
   {
      alert("\n\n Your E-mail address is invalid.");
      return false;
   }
   else if (ck==-5)
   {
      alert("\n\n Your E-mail address is incomplete.");
      return false;
   }}
   return true;
}