I use my phone a lot to browse Reddit, and sometimes I click a link to a Tumblr blog and get redirected to an ad site.
Then I wonder, Why hasn’t the post been removed as spam? The answer, after some investigation, is that the blog only redirects on mobile devices. People on desktop and laptop computers have no idea.
To find out if a blog is doing this, you can view the source code for the page. (How to do this depends on the browser you’re using.) Near the beginning, you’ll find code that looks like this:
To make this easy, you can search for “DM_redirect”. Basically, what this does is check if the user is using a mobile browser and redirect to “somesite.example.com” if they are. This site is the ad site.
If you find one of these blogs, report it! To do this, search for the blog name. When the blog comes up, click the person icon in the upper right and then “Flag this blog.” Report the blog as spam, because that’s what it is.