Yes, there were either two errors in the original (thinking that <code> tags get output and that ".X" selects <X> tags) or just one typo (writing ".pre" instead of "pre"). Since the node was about <pre> tags, I just assumed the former and didn't go look up CSS selector syntax.
To collapse the overlapping corrections from multiple replies, you'd want selectors of ".code" (class="code") and "pre" (<pre>) to get both types of blocks.
and it seems the code tags get output as pre blocks with that class
Sure, it seems that way to you. :) But PerlMonks <code> blocks are not output as <pre> blocks for me (because I mostly browse PerlMonks with a browser that has supported the standard soft hyphen (­) for years, unlike FireFox, and so I can use "auto code wrap"). So it is better to use ".code" for selecting code blocks than "pre" (especially since the next major release of FireFox will finally support ­ properly and "auto code wrap" rocks compared to fixed-width code wrapping so many will likely enable it.