Might depend on the browser, but Webkit-based browsers, for example, use a 0xffffff mask on the resulting specificity. And so... $ python >>> MASK = 0xffff

Might depend on the browser, but Webkit-based browsers, for example, use a 0xffffff mask on the resulting specificity. And so... $ python >>> MASK = 0xffffff >>> MASK 16777215 >>> ID = 0x10000 >>> ID * 256 16777216 >>> ID * 256 & MASK 0