White box in navigational menu after clicking

That’s normal. What you’re seeing is a white/gray border which shows up to let you know you’ve either clicked or hovered over an item. Also called “Focus” Most sites have this as it helps to indicate that an action is taking or has taken place. You can always change the color if you want, or you can set it to 0px instead of 1. That would remove it from showing.

/* Display outline on focus */
:focus {
	color: #333;
	outline: #ccc solid 1px;
}

On the default Theme’s CSS file it is located at line 1167, but it may be on a different line in your code. Just search for the above code and change it to 0px.

Try and reload the page and see if it shows up normally. If not, I’ll re-post it again.