Board Thread:Support Requests - Getting Technical/@comment-25587511-20141027112133/@comment-2170536-20141027181626

You could definitely show/hide things based on username using JavaScript/CSS, but as Tupka217 said it would still be visible in the page source if someone wanted to peek. If you have honest players you could simply set up collapsed tables or div elements with a 'GM information' heading to indicate spoilers that players shouldn't be reading.