How to show popup message using CSS and jQuery?

Here’s how  does it:

This is the markup, initially hidden so we can fade it in:

<div id='message' style="display: none;">
    <span>Hey, This is my Message.</span>
    <a href="#" class="close-notify">X</a>
</div>

Here are the styles applied:

#message {
    font-family:Arial,Helvetica,sans-serif;
    position:fixed;
    top:0px;
    left:0px;
    width:100%;
    z-index:105;
    text-align:center;
    font-weight:bold;
    font-size:100%;
    color:white;
    padding:10px 0px 10px 0px;
    background-color:#8E1609;
}

#message span {
    text-align: center;
    width: 95%;
    float:left;
}

.close-notify {
    white-space: nowrap;
    float:right;
    margin-right:10px;
    color:#fff;
    text-decoration:none;
    border:2px #fff solid;
    padding-left:3px;
    padding-right:3px
}

.close-notify a {
    color: #fff;
}

And this is javascript (using jQuery):

$(document).ready(function() {
    $("#message").fadeIn("slow");
    $("#message a.close-notify").click(function() {
        $("#message").fadeOut("slow");
        return false;
    });
});

And voila. Depending on your page setup you might also want to edit the body margin-top on display.