Even if Java is installed, you must enable its use within your browser. To do so, check your preferences menu. The option is called Enable Java and is found within the "Content" or "Advanced" menus.
- KDE Konqueror
To enable Java in the KDE Konqueror browser, make sure that the Java preferences are enabled and that Use KIO is checked. In the box that specifies the path to the java executable, simply typing java often works better than the full path to the executable.
Java 1.6.0 Update 03 and 04
Some people experience problems that result from using newer web browsers like Firefox 18.104.22.168 with Java version 1.6.0 Update 03 or 1.6.0 Update 04. Often, switching to an earlier version of Java (e.g. 1.6.0 Update 02) solves these problems.