CSS “and” and “or”

&& works by stringing-together multiple selectors like-so:

<div class="class1 class2"></div>

div.class1.class2
{
  /* foo */
}

Another example:

<input type="radio" class="class1" />

input[type="radio"].class1
{
  /* foo */
}

|| works by separating multiple selectors with commas like-so:

<div class="class1"></div>
<div class="class2"></div>

div.class1,
div.class2
{
  /* foo */
}