function cm_is_email (address) {   
       if(cm_is_empty(address)) return false; 
       if(cm_have_whitespaces(address)) return false;
       
       var i = 1;
       var addressLength = address.length;
       var fuera = false;
       var car = "";

       // Mirando por la @
       while (!fuera) {
         if(i < addressLength) {
         car =  address.substring (i, i+1);
             if(car == "@") fuera=true;
         } else { fuera = true; }
         i++;
       } 

       if (i >= addressLength) { return false; } 
       if (car != "@") { return false; } 
       i++;

       // Mirando por el .
       fuera = false;
       car = "";
       while (!fuera) {
         if(i < addressLength) {
             car =  address.substring (i, i+1);
             if(car == ".") fuera=true;
         } else { fuera = true }
         i++;
       } 
       if (i >= addressLength) { return false; } 
       if (car != ".") { return false; } 
       return true;
}

function cm_is_empty(variable) { 
        if((variable == null) || (variable.length == 0) || (variable.value == "")) { 
          return true; 
        }
        return false;
}

function cm_have_whitespaces(variable) {   
       var espacio = " \n\t\r";
       var i;
       for (i = 0; i < variable.length; i++) {   
           var car = variable.substring (i, i+1);
           if (espacio.indexOf(car) != -1) return true;
       }
       return false;
}

function teclaPresionada(e){
    if(window.event){
        keynum = e.keyCode
    }else if(e.which){
        keynum = e.which
    }
    return keynum;
}

function showError(_field){
	$('#'+_field).addClass("input_error");
	document.getElementById('error_'+_field+'_req').style.display="block";

}