The most common cause for this problem is if your web browser is not configured touse the JVM plug-in.

I am assuming that you are using the JDK from Sun and Internet Explorer. When you installed the JDK when it reached the point to install the JRE you should have been prompted to say if you want to use the JVM with your web browser.

If you did not take this option you should be able to find Java in Control Pannel and re-enable the association.