If you are using a website builder or have written the code for your website from scratch, it is still nice to periodically take a snapshot of how the website looks and functions on the live web. The following are three options for doing just that.
Twitter has the internal ability for a user to download their entire Twitter archive. This includes all Tweets (and retweets) for the entire time the account has been active. The download allows for targeted searching of the Tweets using keywords, hashtags and usernames and the ability to organize the Tweets by month.
You can find more information about how to utilize this Twitter functionality in the Your Twitter Archive blog post.
Facebook allows you to download your own Facebook data via the account setting "Download a copy of your Facebook data." It is important to note that this download only includes photos and videos that you have shared; wall posts, messages and chat conversations from your user account; your friends' names and some email addresses (depending on the privacy settings your friends have on their accounts). You cannot download friends' photos and status updates, other people's personal information, or comments you have made on someone else's post.
You can find more information about how to use the Facebook feature by visiting Facebook: Downloading Your Info.
Instagram does not have internal functionality that allows for a user to download and archive all of their content. However, Instaport is third party software that allows a user to download all of their videos, pictures and posts.
Many Blog sites have some export functionality built in that allows content creators to download posts, pages, comments, categories and tags.