Meta viewport tag seems to be ignored completely or has no effect

It is working! On your page you are using:

<meta content="width=640, initial-scale=0.47, maximum-scale=1.0, user-scalable=1" name="viewport">

When I open the page on my phone (ios7 iphone5) I see exactly the right result.

Are you 100% sure you really tried putting the following in your code?

<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">

It doesn't get ignored.

UPDATE1

I just saw that in your code it seems you are using my second viewport but i gets changed probably by javascript to the 640px viewport. Thats maybe the reason why for you it feels like it gets ignored. Because during runtime the viewport gets changed...

UPDATE2

Ok found the problem.

function updateWidth(){
    viewport = document.querySelector("meta[name=viewport]");
    if (window.orientation == 90 || window.orientation == -90) {
        viewport.setAttribute('content', 'width=1401, initial-scale=0.34, maximum-scale=1.0, user-scalable=1');
    }
    else {
        viewport.setAttribute('content', 'width=640, initial-scale=0.47, maximum-scale=1.0, user-scalable=1');
    }
} 

Your page is calling this function which overrides your viewport. Did you know about that function?

I know this is a hella old question now but it was the first result in Google when I had this issue so thought I'd update in regards to iOS 10.

It seems Apple now completely overrides the user-scalable=no in iOS 10 in order to improve accessibility

See: Thomas Fuchs' Twitter Post

You should try, as a workaround, the following code:

html { 
    zoom: .8; 
}