Combining two or more CSS selectors with a boolean condition
These should work:
&& = div.message.error {}
|| = div.message, div.error {}
Don't think you can do "not"
Edit: Just did a quick test to confirm:
<html>
<head>
<style type="text/css">
div.error.message {
background-color: red;
}
div.message, div.error {
border: 1px solid green;
}
</style>
</head>
<body>
<div>None</div>
<div class="error">Error</div>
<div class="message">Message</div>
<div class="error message">Error Message</div>
</body>
</html>
The "message", "error" and "error message" divs all have a green border and only the "error message" div has a red background.
Try div.message.error
.