This first happened a few months ago and @thomthom got it fixed.
But it has resurfaced !
There’s a Trimble linked image to the right-hand end of the top-banner of the http://ruby.sketchup.com/ pages.
That image [ https://www.sketchup.com/sites/develope … -white.png ] is not found, and as a result the default place-holder is making the top-banner deeper because the default place-holder is larger.
As a result the top part of the main page is covered over by the top-banner…
Preventing the top-left links being seen/clicked.
The broken-link place-holder in Firefox and IE is quite large, but in Edge and Chrome they are much smaller, and so then they avoid this total ‘overlapping’.