Why is element in the tab sequence in ember application. clean to make address bar not in the tab sequence

I have a really simple form in Ember.js which has 3 form elements. But the tab will go through 5 element and an element I can't see, I used document.activeElement in console, then I got a element, it doesn't have a tabindex attribute. Is there anyone know why the element in the tab sequence? And also, what's the most clean way to skip the address bar(url field) in the tab sequence. Thanks.