This property returns a value only when the user reaches the current page through a link from the previous page. Otherwise, document.referrer returns an empty string; it also returns an empty string when the link is from a secure site.For example, if PageA.htm includes a link to PageB.htm, and the user clicks that link, the document.referrer on PageB.htm returns "PageA.htm". However, if the user is on PageA.htm and types PageB.htm into the address line or uses Open in the File menu to get to PageB.htm, the document.referrer returns an empty string.
能解释一下为什么要放到web服务器吗?答案最好用中文吧,我的英语水平不是很好。谢谢。