stackoverflow works but my site doesn't

I have an About button:

    $('#btnAbout').button().click(function () {
    // var newURL = "https://substantiator.com/Help/html/Introduction.html/";
    var newURL = "http://stackoverflow.com/";
     chrome.tabs.create({ url: newURL });
});

When I use a link to go to stackoverflow it works fine. But when I try to go to my page  I get a 404 error. 

The address in the browser shows:

https://substantiator.com/https://substa...tion.html/

what's going on?

proof that an old dog can learn new tricks