I would like to trigger WP_Query if a particular <div> is visible to the users. In other words, I want to load the posts via WP_Query when a <div> is visible.
Here is a live example: http://androidpolice.com - click on the top menu (Apps/Games) then you can see their logo and after awhile the posts are loaded.
Is this possible? If so, how?
This can be done by creating a method to execute the WP_Query somewhere in your functions.php. This method can be called with an ajax call from a js file. The js file contains a onclick or bind method to trigger the ajax call. The user clicks on the menu item and the onclick is fired.
Smashing magazine provides a fine tutorial http://www.smashingmagazine.com/2011/10/18/how-to-use-ajax-in-wordpress/