you dont always need to create a .jar file.
If you are running an applet, make sure all the class files are in the same folder as your page, and include the following code to embed it:
CODE
<applet
code = "main.class"
width = "300"
height = "300"
>
</applet>
For the code = "main.class" part, change the word "main" to the name of your client class or interface.
As long as the .class files and the webpage file are in the same folder, you shouldnt have a problem. The .class files will be able to interact with each other without problem as long as they are together.
If you dont have a crazy large project, it is an easy way to embed Java Applets.