说明：  Delphi判断网址是否存在，检查输入的URL网址是否可以打开，将使用Delphi中的TNMHTTP控件的head方法来检查网址是否有效。从运行截图你可以看出，程序会返回不同的结果，比如是否正确解析地址、是否能够连接到主机、是否存在这个页面等，以此几方面来综合判断，该网址是否可以正确被访问。
(The Delphi judge the existence of Web site, check whether the input of the URL web site can open, head will use Delphi s TNMHTTP control to check the effectiveness of the web site. Running from the screenshot you can see, the program will return different results, such as whether the correct address resolution, will be able to connect to the host, the existence of this page, this several aspects to comprehensive judgment, whether the URL can correctly be accessed.)