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IE 9 faster but wrong JavaScript

Microsoft released their new preview version 7 of Internet Explorer 9, with benchmark (one benchmark) results stating IE is the fastest browser (JS execution) now.

In fact, as Rob Sayre points out, heir JS optimizations produce invalid JS results, also pruning or removing code where something else is supposed to be executed. They missed the side-effects of the heavily dynamic JavaScript language.

A commentator on that post also points out Microsoft mistakes the term Dead Code for Inefficient / Useless Code making their statements about optimization false.