Error 429 Too Many Requests in Google Chrome

I started getting 429 Too Many Requests error on different sites. I see it quite often only in the Google Chrome browser. Tried Opera, everything works fine there. Even if there is no error, it can take quite a long time to load one or some of the sites. What does it mean, too many requests? Is it something on my part or not? – This is the main question.

AuthorZac Turner