To avoid flickering when you try hiding elements with Optimizely, inject css styleheads into the head element instead of using Javasript to apply css to each element.

code.js

/* _optimizely_evaluate=force */
$('head').append('<style type="text/css">.something {display:none !important;}</style>');
/* _optimizely_evaluate=safe */
$('head').append('<style type="text/css">.something {display:none !important;}</style>');