a quick glance at the browser inspector will show the source of the problem along with a solution
there is an ad element with a fixed height, which pushes the menu down
deleting or hiding the element moves the menu back in place (assuming this is where it's supposed to be, looks a bit too high now)
this explains why some users dont see the issue, their particular adblocker is removing the element by its class name ('ad')
user workaround 1: adjust adblocker settings to specifically hide that header ad element
user workaround 2: open the inspector to delete or hide the element as needed if it's in the way of something important
stardock easy fix 1: increase the header height
stardock easy fix 2: remove the ad from the header's html, is that even the right position? it looks like it will cover up the logo
stardock medium fix: maybe it's supposed to show up below the logo so the menu+content is further down? then fix the html/css, it's quite basic, give the ad an absolute position then increase the header height along with the menu's top position
