If you look at the theme I use, some posts are smaller than others. In order to achieve that, I tag them with “xs” (then they display as a small one column box). I could also do an “xl” post and then it would occupy the whole width of the screen. I never do that because I have nothing so important to say that it should assault people’s eyeballs with it.
Also, I reserve “xs” posts for small stuff, mainly a photo without much text or a one line comment. If you access my Tumblr from outside your dashboard (meaning, through the page itself), you will see that these tags are invisible then. They serve a functional purpose for my posting only.
For the past decade and a half I have been making all my content available for free (and never behind a paywall) as an ongoing practice of ephemeral publishing. This site is no exception. If you wish to help offset my labor costs, you can donate on Paypal or you can subscribe to Patreon where I will not be putting my posts behind a lock but you'd be helping me continue making this work available for everyone. Thank you. Follow me on Twitter for new post updates.