I went to load up one of my projects that I have been working on for quite some time, and all I come back to is sections of random block have gone missing :/ I don't know what applies to these worlds for them to break, but most of the world went missing.
Image will explain a bit
Taken from mojang.com :
"If you are updating from 14w26a or 14w26b, your saved world has corrupted blocks and it will be heavily damaged once you open it in 14w26c. Please use a world backup that was saved with a pre-14w26 version.
Never use snapshots without first making backups of your saved worlds."