We have given our alert and confirm box, look similar to that on Facebook. You can very easily customize it as per you website's interface, by doing some minor changes in the CSS. This is the simplest way to implement this.
We have used a small CSS to style the Popup box which appears on the click event. Below is the CSS code.
So this was it, a very simple way to customize the look and feel of your alert and confirm boxes as per your website's theme. Do experiment with the CSS, to create even more interesting Alert and Confirm boxes. For any problem, please comment.