mouse clicked in web applications

Hi everybody, I am developing an ASP.NET application using C# and GDI+. The application interface contain a group of rectangles, where each rectangle, once clicked, should display some related information. This is possible in a Windows application by writing: private void MouseClicked(object sender, System.Windows.Forms.MouseEventArgs e) { if(e.Button == MouseButtons.Left) { if (Rectangle.Contains( new Point(e.X, e.Y))) {.......................... But what about a web application? How do I determine wether a mouse was clicked inside a rectangle?? Please help me!!!