If you are looking for quick way of alerting users, this code is perfect for you. Be careful not to over use this mouseover javascript alert box, as it may irritate your users, and cause them to leave your website.
Example Mouseover alertTo you this Javascript copy and paste the following html code into your web editor and change the parts in red to suit your needs.
<a href="" onMouseOver="alert('Your Pop-up Message');return true;">Link Text</a>