3.1. Código

$(function(){

    var LoginError;
    var DivX = "<div class=\"x\" onclick=\"$('#ELogin').fadeOut(1000);\">X</div>";
    var CheckLoginUser;
    var CheckLoginPass;
    var LoginUserName       = $('#LoginUserName');
    var BoxLoginUserName    = $('#BLUserName');
    var BoxLoginPassWord    = $('#BLPassWord');
    var LoginPassWord       = $('#LoginPassWord');
    var BoxError            = $('#ELogin');

    setInterval(function(){
        CheckLoginUser = $.ajax({
            url: '/Wibbop-Server/default/submit_login.php?username='+LoginUserName.val(),
            dataType: 'text',
            async: false,
        }).responseText;

        CheckLoginPass = $.ajax({
            url: '/Wibbop-Server/default/submit_login.php?username='+LoginUserName.val()+'&password='+LoginPassWord.val(),
            dataType: 'text',
            async: false,
        }).responseText;

        if (LoginError == false)
            $('#SLogin').fadeIn();

    }, 30);

    LoginUserName.focusout(function(){
        if (LoginUserName.val() == "") {
            BoxError.show();
            BoxError.html("El nombre de usuario está vacío "+DivX);
            BoxLoginUserName.css('box-shadow','0 0 5px 1px #d43f3a');
            BoxLoginUserName.css('border-color','#d43f3a');
            LoginError = true;
        } else if (CheckLoginUser == "error-true") {
            BoxError.show();
            BoxError.html("El usuario no existe "+DivX);
            BoxLoginUserName.css('box-shadow','0 0 5px 1px #d43f3a');
            BoxLoginUserName.css('border-color','#d43f3a');
            LoginError = true;
        } else {
            BoxLoginUserName.css('box-shadow','0 0 5px 1px #3589A3, inset 0 0 1px #A5D3E0');
            BoxLoginUserName.css('border-color','#3589A3');
            BoxError.hide();
        }
    });

    LoginPassWord.focusout(function(){
        if (LoginPassWord.val() == "") {
            BoxError.show();
            BoxError.html("La contraseña está vacía "+DivX);
            BoxLoginPassWord.css('box-shadow','0 0 5px 1px #d43f3a');
            BoxLoginPassWord.css('border-color','#d43f3a');
            LoginError = true;
        } else if (CheckLoginPass == 'error-true') {
            BoxError.show();
            BoxError.html("Los datos no coinciden "+DivX);
            BoxLoginPassWord.css('box-shadow','0 0 5px 1px #d43f3a');
            BoxLoginPassWord.css('border-color','#d43f3a');
            LoginError = true;
        } else {
            BoxLoginPassWord.css('box-shadow','0 0 5px 1px #3589A3, inset 0 0 1px #A5D3E0');
            BoxLoginPassWord.css('border-color','#3589A3');
            BoxError.hide();
            LoginError = false;
        }
    });

});