Many web sites like Facebook and LinkedIn have implemented an « infinite scrolling » view: when you reach the bottom of the content area, more articles are dynamically loaded and the page's height changes. I won't go into the details or accessibility of such a design, but I want to list here one of its bad and painful side-effect on another area of the page, the page's footer...

Both Facebook's and LinkedIn's web sites show a page footer with several links:

Facebook's footer

LinkedIn's footer

Here, the dynamic data are loaded so fast I don't have the time to read the footer to find the link I want before it goes away, pushed outside of the viewport by the newly inserted content! Extremely painful.

And when a webdesign flaw makes vital (to the user) information unreachable, it's then a functional flaw.

Update: someone just asked me how I did the two screenshots above. Excellent question, indeed... I had to use the PageSaver add-on to Firefox... Using screencapture on my Mac was a no-go, the page update was too fast...