JavaScript is not JAVA, but rather a lite weight cousin. Javascript is built into the browsers supporting it. Although javascript can be powerfull, you'll find it's support, minimal in early browsers. This un-even support means that unless you are going to ignore early browser users, you can only use a sub-set of the language, or you must detect the capabilities on-the-fly. JAVA and Javascript in all their forms is an incrediable concept in portable software. The major consideration is the trade-off between amazing capability and download time. Only experiamentation will give you the understanding of the balance to use