I’ve been informed that Tumblr has recently started putting ads in blogs, which is messing up themes and generally being annoying. This can be shut off, but the option is buried a bit. To shut down ads on your blog, do the following:
Account options (person symbol in the top right) -> Settings (cog symbol) -> Select the blog in question on the right -> Scroll down to Advertising toggle -> toggle off.
You will need to do this for all of your blogs.
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