我在Windows 7 Pro上运行XAMPP。我正在尝试设置一个虚拟主机，这样当我使用“dev.app“作为域时，我就可以直接进入laravel安装的公共文件夹。
Laravel位于F:/xampp/htdocs/dev/public
我打开了位于F:\xamp\apache\conf\extra\https-vhosts.conf的httpd-vhosts.conf文件
把所有东西都换成了这个

# Virtual Hosts
#
# Required modules: mod_log_config

# If you want to maintain multiple domains/hostnames on your
# machine you can setup VirtualHost containers for them. Most configurations
# use only name-based virtual hosts so the server doesn't need to worry about
# IP addresses. This is indicated by the asterisks in the directives below.
#
# Please see the documentation at 
# <URL:http://httpd.apache.org/docs/2.4/vhosts/>
# for further details before you try to setup virtual hosts.
#
# You may use the command line option '-S' to verify your virtual host
# configuration.

#
# Use name-based virtual hosting.
#

NameVirtualHost *:80

#
# VirtualHost example:
# Almost any Apache directive may go into a VirtualHost container.
# The first VirtualHost section is used for all requests that do not
# match a ##ServerName or ##ServerAlias in any <VirtualHost> block.
#

<VirtualHost localhost>
    DocumentRoot "F:/xampp/htdocs/"
    ServerAdmin admin@localhost

    <Directory "F:/xampp/htdocs/">
        Options Indexes FollowSymLinks
        AllowOverride all
    </Directory>

</VirtualHost>

# Development
<VirtualHost dev.app>
    DocumentRoot "F:/xampp/htdocs/dev/public"
    ServerAdmin admin@localhost

    <Directory "F:/xampp/htdocs/dev/public">
       AllowOverride All
       Order Allow,Deny
       Allow from all
       Require all granted
    </Directory>
</VirtualHost>

然后我打开位于C:\Windows\System32\drivers\etc的主机文件，并将localhost行更改为如下所示

127.0.0.1       localhost      dev.app
127.0.0.1       127.0.0.1

但是，当我dev.app在浏览器中转到www.example.com时，出现此错误
无法联机
Firefox无法在app.dev建立与服务器的连接。

The site could be temporarily unavailable or too busy. Try again in a few moments.
If you are unable to load any pages, check your computer's network connection.
If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web.

我错过了什么？我做错了什么？

**注意：**我在更改vhosts文件后重新启动了Apache。另外，我更新了laravel的config文件夹中的app.php文件，使url中有http://dev.app值。
已更新在添加http：//....后，网站已解决，但图像未显示。