The Author's Note
In a lot of stories, there are these small paragraphs, maybe even just one or two sentences that are bolded and even sometimes italicized. It's obviously completely different from the rest of the story, which means... SOMETHING IMPORTANT.
Do not ignore author's notes. Author notes are extremely important. They might advise you to listen to a certain song to set the mood, warn you that there is sexual content ahead, or might just be a quick apology for a late update. Either way, it's important. It's bolded, come on. Nothing says "THIS BE IMPORTANT" like bold letters.
And if you're writing the author's note, don't tell the reader your life's story about why you were so late with a chapter. That's what your message board is for. The author's note is for you to provide quick, important information for the reader. Maybe it's a series and you're telling them there's a book before it and that they should seriously read it in order.
Also, never cut halfway into the chapter with an author's note. You've ruined the mood and now the reader is rolling their eyes because you just cock-blocked them. Don't do that. Naughty, author. You let them read until the end, THEN you can tell them whatever it is you want to tell them.
Your author's note should be short, sweet, and to the point. Don't write a whole other book in your author's note. At least, not until the end of the book if you want to let them know "HEY THANKS FOR READING YOU BEAUTIFUL PEOPLE" or whatever. That's fine. But at the end or beginning of a chapter, you have to make your author's note short. No one wants to spend their whole day of reading your author's note. They want to get to the story as quickly as possible.