I did that for a while to hide the random “notifications” from people I had never heard about that appeared every other day on google.com. I had to change the custom style so many times because they changed the ids/classes every other week that now I just logged out of my Google account to not see it.

There's a better way now. Click the notifications bell and then in the popup, click on the gear icon - you can check and uncheck boxes to customize which Google products show notifications there.