Most sites have a favicon, a small symbol to the left of the browser bar that represents the website. When the site is loading data, the favicon is replaced with a spinning disc. This disc behaves differently depending on the stage of the URL search. Initially the disc will appear grey, rolling anti-clockwise. This means the browser is in request mode and data is being called. It will be in one of the following states:
However, when the disc changes to a blue circle rolling clockwise, the browser is in download mode and will be in the one of the following states:
The colour change from grey to blue is incidental as it simply creates a visual point of difference. As you might expect, however, the speed at which the circle rotates – blue or grey – is related to speed of the data retrieval and download.
Sometimes it may seem like the spinning will never end. Don’t worry, you’re not going insane – there is a reason for this! Effectively, the browser is waiting for a response that might never actually come. This can be down to a few things but in short it's anything that interrupts the communication between your browser and the various web resources you’re searching for. Just refresh and repeat.