open_url Command Syntax ?

Hi,
i just looked through the command.txt File and found a Command called open_url
and want to test what it does (I guess you can open a Website Url with this Comannd).

I tested it and it takes 3 Parameters:

#open_url(x,y,z)

But i dont know what i need to enter where :)
Actually i get an "Invalid Name"-Error every Time i want to use this command.

Thanks for your Help ;)

#open_url("username","website")

website as in :

google.com
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not

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