Apple's latest Java update requires you periodically enable the Java plug-in manually. Here is how this works in OS X.

If you still need Java 6 for Web applets after installing Apple's latest updates, there is a way to restore it and override Apple's preference for the use of Oracle's Java 7.

Under Scripting, set Active scripting to Enable, and set Scripting of Java applets to Enable. Click OK to return the Security Settings, then click Apply, and then OK. Internet Explorer 3.x: ...