Prepares a string for use as a valid class name.
Do not pass one string containing multiple classes as they will be incorrectly concatenated with dashes, i.e. "one two" will become "one-two".
$class: The class name to clean.
The cleaned class name.
function drupal_html_class($class) {
return drupal_clean_css_identifier(drupal_strtolower($class));
}