My template keeps disappearing

I have created a website www.codnor.info using the essence template. However occasionally when I view or work on my site, I find that the template has disappeared leaving just my site content on screen. I usually solve this by closing the site then opening it again. But it also happens when viewing the site from other peoples computers, Clicking refresh usually cures the problem. This can happen on any or all of the pages, please advise how to help.
Regards Stuart
 
sad I’m frustrated
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