lucy24 - 8:22 am on Sep 23, 2012 (gmt 0)

When do you think will the layout: box (or rather the the layout: flexbox ) -command be supported by the modern browsers without prefix?

Doesn't matter, really, unless your audience is composed 100% of people who always use the latest hot-off-the-presses browser. (Considering the range of browsers used even by WebmasterWorld members, I really really doubt this.)

What you need to do is use the vendor-specific forms in addition to the bare form. Eventually most browsers will recognize the default form; but you should keep the extension several years longer for backward compatibility.