http://www.flickr.com/help/general/#1
Flickr is the best way to store, sort, search and share your photos online. There is a huge mass of photos in the world, and Flickr provides a way to organize yours, and for you and your friends and family to tell your stories about them.
Behind it is AJAX:
AJAX–Asynchronous JavaScript and XML–is a web development technique for building interactive web applications so they behave more like regular software that resides on your PC. Some examples of AJAX in use include Google Maps and photo-sharing site Flickr.
Footer