Option1. you can use AlertifyJS , this is good for alert


Option2. you start up or just join a project based on webapplications, the design of interface is maybe good. Otherwise this should be changed. In order to Web 2.0 applications you will work with dynamic contents, many effects and other stuff. All these things are fine, but no one thought about to style up the JavaScript alert and confirm boxes.
Here is the they way
create simple js file name jsConfirmStyle.js. Here is simple js code
ie5=(document.getElementById&&document.all&&document.styleSheets)?1:0;
nn6=(document.getElementById&&!document.all)?1:0;
xConfirmStart=800;
yConfirmStart=100;
if(ie5||nn6) {
if(ie5) cs=2,th=30;
else cs=0,th=20;
document.write(
"<div id='jsconfirm'>"+
"<table>"+
"<tr><td id='jsconfirmtitle'></td></tr>"+
"<tr><td id='jsconfirmcontent'></td></tr>"+
"<tr><td id='jsconfirmbuttons'>"+
"<input id='jsconfirmleft' type='button' value='' onclick='leftJsConfirm()' onfocus='if(this.blur)this.blur()'>"+
" "+
"<input id='jsconfirmright' type='button' value='' onclick='rightJsConfirm()' onfocus='if(this.blur)this.blur()'>"+
"</td></tr>"+
"</table>"+
"</div>"
);
}
document.write("<div id='jsconfirmfade'></div>");
function leftJsConfirm() {
document.getElementById('jsconfirm').style.top=-1000;
document.location.href=leftJsConfirmUri;
}
function rightJsConfirm() {
document.getElementById('jsconfirm').style.top=-1000;
document.location.href=rightJsConfirmUri;
}
function confirmAlternative() {
if(confirm("Scipt requieres a better browser!")) document.location.href="http://www.mozilla.org";
}
leftJsConfirmUri = '';
rightJsConfirmUri = '';
/**
* Show the message/confirm box
*/
function showConfirm(confirmtitle,confirmcontent,confirmlefttext,confirmlefturi,confirmrighttext,confirmrighturi) {
document.getElementById("jsconfirmtitle").innerHTML=confirmtitle;
document.getElementById("jsconfirmcontent").innerHTML=confirmcontent;
document.getElementById("jsconfirmleft").value=confirmlefttext;
document.getElementById("jsconfirmright").value=confirmrighttext;
leftJsConfirmUri=confirmlefturi;
rightJsConfirmUri=confirmrighturi;
xConfirm=xConfirmStart, yConfirm=yConfirmStart;
if(ie5) {
document.getElementById("jsconfirm").style.left='25%';
document.getElementById("jsconfirm").style.top='35%';
}
else if(nn6) {
document.getElementById("jsconfirm").style.top='25%';
document.getElementById("jsconfirm").style.left='35%';
}
else confirmAlternative();
}
Create simple html file
<html>
<head>
<title>jsConfirmSyle</title>
<meta http-equiv="Content-Style-Type" content="text/css" />
<meta http-equiv="Content-Script-Type" content="text/javascript" />
<script type="text/javascript" src="jsConfirmStyle.js"></script>
<script type="text/javascript">
function confirmation() {
var answer = confirm("Wanna visit google?")
if (answer){
window.location = "http://www.google.com/";
}
}
</script>
<style type="text/css">
body {
background-color: white;
font-family: sans-serif;
}
#jsconfirm {
border-color: #c0c0c0;
border-width: 2px 4px 4px 2px;
left: 0;
margin: 0;
padding: 0;
position: absolute;
top: -1000px;
z-index: 100;
}
#jsconfirm table {
background-color: #fff;
border: 2px groove #c0c0c0;
height: 150px;
width: 300px;
}
#jsconfirmtitle {
background-color: #B0B0B0;
font-weight: bold;
height: 20px;
text-align: center;
}
#jsconfirmbuttons {
height: 50px;
text-align: center;
}
#jsconfirmbuttons input {
background-color: #E9E9CF;
color: #000000;
font-weight: bold;
width: 125px;
height: 33px;
padding-left: 20px;
}
#jsconfirmleft{
background-image: url(left.png);
}
#jsconfirmright{
background-image: url(right.png);
}
</style>
<p>
<a href="#" onclick="javascript:showConfirm('Please confirm','Are you really sure to visit google?','Yes','http://www.google.com','No','#')">JsConfirmStyled</a> </p>
<p><a href="#" onclick="confirmation()">standard</a></p>
</body>
</html>