a class

in your stylesheet you can declare a class as follows:

.info
{
    BACKGROUND-COLOR: black;
    COLOR: aqua;
    FONT-SIZE: 7pt;
    FONT-WEIGHT: normal
}

and then set a link to <a class="info">? What about onMouseover and so on?

you can use the class in any tag

<td class="info">blablabla</td>

the following will underline your link if you put your cursor over it ie. hover

A:hover
{
    COLOR: #4a8c9c;
    TEXT-DECORATION: underline
}

can I have more than one class then`?

.info
{
    BACKGROUND-COLOR: black;
    COLOR: aqua;
    FONT-SIZE: 7pt;
    FONT-WEIGHT: normal
}

.main
{
    BACKGROUND-COLOR: white;
    COLOR: red;
    FONT-SIZE: 12pt;
    FONT-WEIGHT: normal
}

and then place it like

<a class="info">
and
<a class="main">
to different places on the page`?

yes