Q:

Is it possible to have a code block that isn't highlighted?

There are some languages that get highlighted incorrectly. Is it possible to specify a code block that does not have any highlighting when it gets displayed?
Here is an small example of CSS that is getting highlighted as if it was C/C++.
#div.a {
  background-color: #000000;
}

.static {
}

A:

You can display a block without color by using a <pre> block.

#div.a {
    background-color: #000000;
}

.static {

}

And I think StackOverflow is using Google Code Prettify, but I haven't figured out how to get it to show CSS yet (though it claims it should, attaching class="prettyprint lang-css" in a pre tag doesn't seem to work.).
CORRECTION: Oops, apparently StackOverflow uses Google Code Prettify not syntaxhighlighter as was previously posted, thx for the correction shog9, it's always nice to have the right information.  Despite the correction, the class="prettyprint lang-css" attribute still doesn't seem to work, even with supported languages such as C.

A:

Actually, it's Google Code Prettify. 
As Akdom noted, you can just use a <pre> tag and leave out the prettyprint class to get a plain ol' code listing. Alternately, we support special comment prefixes to force language-specific highlighting (or turn highlighting off altogether):
<!-- language: lang-css -->

...will properly highlight CSS syntax, while
<!-- language: lang-none -->

...will turn it off.

