Webchunks (the Firefox add-on) lets you select an arbitrary element in a web page to turn it into a webchunk. Nothing magical here. A Webslice is, per Microsoft's "spec", an element carrying an ID and the class slice. In other terms, an element selected by the selector #thatID.slice. Webchunks just extends that notion to be able to use here any CSS selector, not only that one.

But selecting an arbitrary element can lead to unexpected results. Let's take a concrete example :

  • the web page liberation.fr has a block of recent news on the right hand side ("Dernières Dépêches")
  • that block can be selected using the selector #e1b3-1
  • but the contents of that block are not available at load time but rather ajax-based...
  • so comparing a cached version of that element and a recently downloaded version is meaningless if you don't let all JavaScript code in the page run and compare them only afterwards...

I am then unable to say liberation.fr updated its Last News section just loading the source of that HTML page... Painful.

Conclusion : I miss here something standard (an attribute, a class, whatever and I don't care) in the DOM to let me know the contents of that element are retrieved over the wire after page load. I also miss a standard event allowing me to know the contents are now loaded and that the "final" content of the element can now be observed.