How to make code for page link using drop down selected con

Question

Hi Friends,
    I m creating one web application my expecting output is



i spliited my page 2 columns right side column has set  drop down menus(constant)
depends on the selection that page ll load on left side column


ref:

http://www.dyngeometry.com/web/WorldRegion.aspx


Kindly do the need full!

Thanks & Regards

Rocky