AutoPager is a firefox extensions to autoloading next page into the same page when you browse to the bottom of the page. It’s configuration is base on XPath. You can find there is a built in function to create a XPath by click on the page. And you can find XPath tutorials at http://www.w3schools.com/xpath/ and http://www.zvon.org/xxl/XPathTutorial/General/examples.html.
You can import some sample configuration from http://blogs.sun.com/wind/resource/autopager.xml. It includes the settings for google search ,google image search ,yahoo search and addons browser at addons.mozilla.org. It also support update settings from the comments at http://blogs.sun.com/wind/entry/autopager_site_config. If you have new site config please export and post to that page. Thanks.