Question: I am making a website which involves lot of computing at the back end...I'm using Java Script at the front end and Java for the back end. Could there be any security problems because of Java Script or can I use any better front end instead of Java Script to make website better?

Answer: 
The biggest potential security problem with Javascript has nothing to do with Javascript (and also applies for "dumb" websites): If you think that the end user will only use your "official" client code, and as a result blindly trust the Javascript code with security-relevant information, then you have a security problem.

* You need to validate all data on the server. The user can make his browser send whatever data he wants, whenever he wants. He does not even have to use a browser (could be a completely hacked-together tool).
* You must not put "secret" data into the client code. Even if it is not directly visible in the browser, the resourceful user can see it.
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Not intrinsically. You could introduce security problems by writing insecure code, but that is try of any language.

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> can I use any better front end instead of JavaScript to make website better?
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Other options for client-side programming require browser plugins (such as Flash) or specific browsers (such as IE for VBScript).

You might not need any client side programming, and any JS you do write should be [progressive](http://en.wikipedia.org/wiki/Progressive_enhancement) and [unobtrusive](http://en.wikipedia.org/wiki/Unobtrusive_JavaScript).