Most of my works lives in a web browser, but I occasionally dabble in Android, WPF, Flex, etc. Every time I go back to working with HTML I am frustrated by its lack of a more powerful layout manager. I am jealous of all the different panel types that other systems offer.
Yes, you can reproduce pretty much any behavior with the right mix of HTML and CSS, but why the hassle? It should be trivial to vertically center some content or dock it to a specific edge/corner. There is too much reliance on fancy nesting or extra helper elements.
Is it an unreasonable wish to see something like this implemented in HTML6 or whatnot? I am aware of stuff like Grid Style Sheets[1], so I know I can't be alone on this one.
[1] http://gridstylesheets.org/