This is a tutorial that will teach you how to get rid of a number next to your messages. Press the flag, and read the text in the speech bubbles. If you are at the website background, and Nano has already said that you have to press the right arrow key to move on, press the right arrow key to get to the next speech bubble. Sorry if it is hard to understand.
Thanks to thriftyfun.com for the cat, and Scratch for everything else! This tutorial was created in Google Chrome version 47.0.2526.106, and it may or may not work in other browsers, or in past/future versions of Google Chrome. Tip: If you are using Microsoft Edge as your browser, then you can simply hover your mouse over your messages, and press F12 on your keyboard to get right to the inspect element screen! (thanks to @CrafterMaster360 for pointing that out to me!)