Javascript is not the same as Java, they are completely unrelated. Javascript is enabled by default on every modern browser, but addons/extensions may change this. Additionally if you are using an older browser, such as Internet Explorer 6 or 7, the javascript may not work. If you are using an older browser, you should upgrade to a more recent browser.
Otherwise we cannot assist you further until you tell us the following information:
1) What Operating System you are using, including the version (e.g. Windows XP, Windows 7, Ubuntu 12.10, Mac OS X Lion).
2) What browser you are using, including the version if applicable (e.g. Internet Explorer 7, Internet Explorer 10, Firefox 22, Safari 6, Google Chrome)
3) What addons/extensions you have installed on the browser