At least 10% of your visitors access your site over a mobile device. They deserve a good experience (and if you provide one, they'll keep coming back). Converting your multi-column layout to a single, linear flow is a good start. But mobile devices are not created equal, and their disparate handling of CSS is like 1998 all over again. Please your users and tame their devices with handheld style sheets, CSS media queries, and (where necessary) JavaScript or server-side techniques.

Semantics in HTML 5

The BBC's dropping of hCalendar because of accessibility and usability concerns demonstrates that we have pushed the semantic capability of HTML far beyond what it can handle. The need to clearly and unambiguously add rich, meaningful semantics to markup is a driving goal of the HTML 5 project. Yet HTML 5 has two problems: it is not backward compatible because its semantic elements will not work in 75% of our browsers; and it is not forward compatible because its semantics are not extensible. If "making up new elements" isn't the solution, what is?