In the shown example, we want a change in text color and a change in font weight to bold on mouse over. Then the CLASS in CSS looks like this:

.HoverDemo:hover {
    font-weight: bold;
    color: magenta;
    background: green;
}

The code for the example looks like this:

Here the text is normal, <SPAN CLASS="HoverDemo">here there is a SPAN with CLASS="HoverDemo",</SPAN> and here the text returns to normal.

On the screen, it looks like this:

Here the text is normal, here there is a SPAN with CLASS="HoverDemo", and here the text returns to normal.