gene c13,630 Points
Where did the nav menu go when the viewport was minimized to medium-size?
And why would the nav menu disappear when the viewport was minimized? How does adding the hamburger menu icon make it visible at a medium-sized viewport?
Randell Purington9,992 Points
It doesn't flow with the rest of the page so it is like it goes away when the viewport reaches a certain width. It is still there but it wouldn't show up on smaller screens such as phones and some tablets.
Christopher Cudiamat6,232 Points
because of this code in the header <header class="navbar navbar-expand-md navbar-dark bg-dark">
the class "navbar-expand-md" indicates that the nav menu will only shows horizontally when the media queries are md(medium) or above and if its below that the hamburger menu will appear instead..
Sylvia Castro9,943 Points
I suggest using the actual CDN from Bootstrap since these files are deprecated