Put the summary of the bug you're having here

What I expected to happen was...:
When I started minecraft for the first time after downloading the new 1.8, I thought the game would look like it always has. Blocks textures go together as normal and everything looking smooth.

What actually happened was...:
When I started playing I clearly noticed black lines between the blocks. It looks awful and I've tried changing all kinds of settings but nothing seems to work. The lines only show on blocks about 10 blocks away from me.

The lines can apear as blue or white as well. This glitch occurs in both single- and multiplayer.

Photos are attached.