If you downloaded and installed one of the beta versions of OS X, chances are that you get regular beta software updates in the Mac app store. When it's a regular update (that is not beta), it's good to update (and highly recommended because many times, there's a security bug fix). However, with beta updates, it's not so important that you update and eventually, it becomes annoying.
A lot of users have complained about this. Getting notifications for every little beta update might be important for developers who produce software for OS X, but for regular users, this is not the case. Beta updates are technically not meant for users. However, what we're talking about a pre-release beta releases that are open for all “eligible” users. Want to turn these beta software update notifications off?
How to Stop OS X Beta Software Update Notifications in Mac App Store
Step #1. Make sure the Mac App Store isn't open. Close it (quit).
Step #2. Click on the Apple Menu -> System Preferences
Step #3. Next, click on App Store
Step #4. There's a button labeled “Change…” next to “Your computer is set to receive pre-release Software Update seeds.” Click on it.
Step #5. Select “Do Not Show Pre-release Updates”
Apple decided to let not just chosen developers but the public as well (regular users) to test their new operating system (OS X 10.10, codenamed Yosemite). A lot of users jumped in on the opportunity. A side-effect of it is that you are also signed up for pre-release beta software updates. These are software updates that Apple wants to test out in the open before making them part of the regular software.
When you turn off the pre-release software update seeds option, you will no longer receive notifications about these updates. However, rest assured that your system will work just fine and you will also get update notifications for major updates that are out of beta.