It's sometimes called a chunk glitch. The chunk won't load sometimes, the best way to fix it is to try relogging, or like post above said, try walking on it.
Use MCEdit to load u world and hit "ctrl+i" and use "repair region", save world and tray if its load the chunk.
If not use MCEdit again and delete the chunk to let MC recreate it on next playing.
If it doesn't work, load up u map that i can tray to fix it.
If not use MCEdit again and delete the chunk to let MC recreate it on next playing.
If it doesn't work, load up u map that i can tray to fix it.