In the Mountain View building complex that houses the main Mozilla offices, there are many doors like this one.

In the Mountain View building complex that houses the main Mozilla offices, there are many doors like this one.

What's your natural reaction to a vertical door handle? You grab it like this...

What's your natural reaction to a vertical door handle? You grab it like this...

...and pull it to open, right?

...and pull it to open, right?

But if the handle is on the inside of the door, then pulling does nothing. EVERY SINGLE PERSON who I've seen encounter these doors has made this mistake.

But if you're on the inside of the door, then pulling does nothing. EVERY SINGLE PERSON who I've seen encounter these doors has made this mistake.

The other side of the building, a few meters away, has doors like this.

The other side of the building, a few meters away, has doors like this.

The outside handle is vertical, the inside one horizontal.

The outside handle is vertical, the inside one horizontal.

Without thinking, you put your hand on it like this, and push. It opens!

When you're on the inside of the door, your natural reaction is to put your hand on it like this, and push.

The architects of the building had a perfect solution to the handle problem, so why did they use it on only half of the doors?

The architects of the building had a perfect solution to the handle problem, so why did they use it on only half of the doors?

Don Norman would not be amused.

Don Norman would not be amused.