Generally it's easier to get away with stealing code since it's not possible to instantly recognize it the way you can recognize stock art and audio, but I'd still be careful with it - if your site has no license information at all anywhere, it's a crappy site. The normal courtesy of giving credit is a notice along the lines of
Using <optional: resource type, e.g. "shader code"> THINGAMAJIG NAME by CREATOR NAME
<URL to the exact page you downloaded it from, or their profile on the site, or their personal webpage>
<optional: "resource used under CC-BY (or other license name that applies) license">