This is really easy with a bit of jQuery.
CSS
div.Message{
display:none;
}
HTML
<div class="Welcome">Welcome to our site<div>
<div class="Message">Thanks for touching me!<div>
jQuery
$('.Welcome').hover(
function () {
$('.Message').show();
},
function () {
$('.Message').hide();
}
);
Example: http://jsfiddle.net/gxn34/
EDIT
To answer your question below
You would need to add the following to your page, usually in the <head>
section
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
And
<script>
$(document).ready(function(){
$('.Welcome').hover(
function () {
$('.Message').show();
},
function () {
$('.Message').hide();
}
);
});
</script>