[DevExpress Support Team: CLONED FROM T324871: AspxDashboardViewer issue with an appended CSS class]
Here you are.
Go to the web page (I'm in IE 11 but the browser probably doesn't matter)
Press F12 to open your Developer Tools window
In the DOM Explorer Window you'll notice Body tag is empty
C lick Fake Dashboard 1. It will take a second and you will get Dashboard was not found. Now this step didn't change Body.
Click Fake Dashboard 2. Bam. You'll notice that a class has been added to the Body and the fonts change etc.
PS. The same steps work in Chrome v48 when viewing the Elements tab