[YouTube-API] need help on YouTube authentication API

I am currently writing a YouTube like web application and ran into some problem with authentication.  I tried using the old ClientLogin api and I kept getting the following error: 

XMLHttpRequest cannot load https://wwww.google.com/accounts/ClientLogin?Email=....&Passwd=...&service=youtube&source=test. Origin null is not allowed by Access-Control-Allow-Origin.

Any idea on how I can solve this issue?

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