Bootstrap 3 modal creates scrollbar when opened

The problem occurred because Twitter Bootstrap always shift the page 15px to the left when a modal is opened. You can solve this by moving the page back to the right - margin-right: -15px. This can be done by using events show.bs.modal and hidden.bs.modal provided by Bootstrap's modal.

$('#myModal').bind('hidden.bs.modal', function () {
  $("html").css("margin-right", "0px");
});
$('#myModal').bind('show.bs.modal', function () {
  $("html").css("margin-right", "-15px");
});

jsFiddle

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FYI:

show.bs.modal: This event fires immediately when the show instance method is called. If caused by a click, the clicked element is available as the relatedTarget property of the event.

hidden.bs.modal: This event is fired when the modal has finished being hidden from the user (will wait for CSS transitions to complete).

Reference

LVarayut's answer sent me in the right direction and what I ended up using is this:

body.modal-open, .modal-open .navbar-fixed-top, .modal-open .navbar-fixed-bottom {
    margin-right: 0;
}

.modal {
    overflow-y: auto;
}