Not sure how closely you are following Internet Explorer 8 development, but they do have one cool new feature called Web Slices. This will let you subscribe to only a section of a web page, and easily delete them when they are no longer needed. You can now use this Internet Explorer 8 feature of the future now in Firefox.
WebChunks is a Firefox 3′s implementation of Microsoft Web Slices. It allows you to “follow” an area of a web page through a dedicated feed bookmarked in a new toolbar. Clicking on the toolbar entry shows the information related to your choice in a popup, without the need to open a complete web page.
Where would you use this in the real world?
Now the famous example of this is eBay. Lets say you wanted to follow an item you were bidding on, but you only wanted to follow the box that had the actual auction information in it. WebChunks allows you to just watch that section. When the auction is over, delete it.
Still lost? Don’t be worried, I was too. Check out the developer’s tutorial on how to use the WebChunks add-on for more information on the idea. For me, this new feature is on the fence of being useful on one side and un-necessary on the other.