Here's a bit of a cheeky question...
You know all those "conversations" us nerds have about scalability and performance where we endlessly debate about where to put business logic and whether scaling the database is easier than scaling the application servers? Well, how come we never end up talking about how to make arguably the most costly (in terms of both time and $$$) operation of our applications perform better?
The costly operation I'm talking about is the journey our markup makes from the web server to the browser. It's funny, because we'll architect fantastic applications, and then shove absolutely bloated junk markup across the vast, unreliable Internet without a second thought. That shit costs money too... (I'm talking about bandwidth). And it's code that's visible to the world.