Client Pull is a method used to give additional instructions to a Web browser that would not have been sent by the server it is currently browsing. Client Pull is not a language, although it is usually implemented using HTML. You probably have seen Client Pull in action but did not recognize it. A common implementation of Client Pull is to have the browser automatically move to a different page without the user clicking a hyperlink.
To understand what goes on in the background of Client Pull, you need to know about HTTP response headers and the <META> tags.
<META HTTP-EQUIV="Refresh" CONTENT="20">
<TITLE>My Home Page (Updates every 20 seconds)</TITLE>
The information on this site changes regularly. For that reason, this page
will reload itself every twenty seconds. If you are not using Netscape or
Internet Explorer, you will need to reload this page manually.<BR>
Server Push is similar to Client Pull in that it also includes extra information within the HTML document. Server Push does not rely on the browser to act on the information included in the document but, instead, relies on the server to push the additional information as scheduled. To understand how Server Push works, we must take a more in-depth look into the MIME standard and specifically the MIME content type multipart/mixed.