These are just tricks and techniques I've used in various places. I believe that most of them are CSS3 compliant.
Here is a way to hide text from visitors until they hover over it.
Here is the CSS:
.spoiler {
color: #fff;
border: dotted 1px #f00;
}
.spoiler:hover {
color: #000;
border: dotted 1px #bbb;
}
And here's how it works in real life:
Who did it? The butler did it.