 <p><code>initial</code> is not supported by IE10</p> <p><a href="https://developer.mozilla.org/en-US/docs/Web/CSS/initial?redirectlocale=en-US&amp;redirectslug=CSS/initial" rel="nofollow">https://developer.mozilla.org/en-US/docs/Web/CSS/initial?redirectlocale=en-US&amp;redirectslug=CSS/initial</a></p> <p>why not use auto?</p>