Spikes and dips in Google Analytics are often caused by specific events. Maybe you released a new website, started a major marketing initiative or your website was unreachable for a few hours. Whatever these case, these spikes and dips in traffic can be difficult to interpret, especially months into the future.
Use Google Analytics Annotate feature to append short notes for any date that had an “Event” that caused traffic to spike or drop. Google lets you easily append your data with annotations that indicate important events, like a new website, a new advertising campaign or a major marketing event.
Make sure your webteam is in the habit of creating annotations for these important events. Go back and add historical events that explain changes in traffic patterns. It is simple to do; simply to go to your account’s Dashboard and click on the hidden little Annotate button and add your events: