It’s working correctly.
The design only changes at 320px wide (iPhone portrait).
If you would like this to occur sooner, you could add:
@media all and (max-width:480px){#hsidebar, header, nav #s, #content, #sidebar, #lsidebar, #rsidebar, footer, #fsidebar{width:470px;max-width:470px;text-align:left;margin-left:auto;margin-right:auto}nav ul.menu{padding-left:0}nav .sub-menu, nav .children{display:none !important}nav ul li a, nav ul li a:hover{width:439px;max-width:439px;border:0;border-radius:0 !important;margin-left:0 !important}nav #s{width:446px !important;margin-bottom:5px}.entry-content{text-align:left}}