There's a nasty bug in Safari that can lead to any static page of your website becoming eventually invisible if your server correctly responds with a 304 code.
I wrote about it 7 months ago, also providing a quick & dirty fix on how you can circumvent it by instructing Safari not to cache your content.
There were quite a few Safari updates in all that time, but for some reason Apple seems to have done nothing about it.
The bug is still there in Yosemite beta and iOS 8(.0.2).
Such a shame!...
I generally like Apple products and do most of my work on an iMac.