Oh jeez, really? A blog post about doing something so easy? Well, yes because it took me about an hour of messing around and so if this helps save one person from the pain, then it’s worth writing. If you’re in a rush or already bored, jump to the short answer.

If you use gmail, you may see the option in the Chat widget to “Call phone”:

Great. Sounds fun, let’s try it:

Oh dear. We don’t have the plug-in installed. We are told “Please download the voice plug-in to make a call.”

Here comes the problem. The link takes you to a download page that has javascript errors preventing your from completing the download:

Refused to display document because display forbidden by X-Frame-Options. Uncaught TypeError: Object [object DOMWindow] has no method ‘onInstallButtonClicked’

Hmm, ok, what next? May I suggest at this point you don’t waste your time trying a different browser, then a different operating system, then a different machine. It’s stupid, you’re not thinking clearly. Take a break and drink some water.

The problem was with the initial link: http://www.google.com/intl/en-GB/chat/voice/. (I assume you will get a different link depending on your language/location.)
Thankfully, a working page does exist, you just have to find it. https://www.google.com/chat/video. Just go there, the page looks different, has no errors, and allows you to call people without resorting to Skype.