Confused About Power Supply

Firstly,

Forgive me. I'm still learning and I've encountered a situation that's a little confusing.

According to the following Arduino Page I should be using a 9V power supply: http://playground.arduino.cc/Learning/WhatAdapter

However, a lot of projects I see use no more than 5V power supplies. Would using the 9V power supply on a project that requires 5V, or less cause a problem?

You need to get to 5V somehow for the 328P/1284P/2560 microcontroller.
You can regulate 7.5V/9V/12V down to 5V with the onboard regulator.
You can apply 5V directly thru the USB connector.
You can apply 5V directly thru the 5V power header.
You can have a standalone design and not even have a 5V regulator on the board, with 5V coming from a regulated wallwart, for example
http://www.dipmicro.com/store/DCA-0520


I use 5V wallwarts all the time to power projects.

Thanks. I'm using the Arduino UNO Rev3. I should have included that.

Does your advice still apply for this board?

I will be using it on a NeoPixel LED strip and I don't want to blow it out.

I just re-read your response. You did actually handle my concerns.

THANKS AGAIN!