Tumblr keeps saying “Invalid HTML” whenever I install a new theme.

There are a couple of things you can try & check before you install a theme to avoid this error. 

  • Have you reset your blog?
  • Did you set any CSS or Javascript in your blog description or modified CSS?
  • Was your internet connection weak when you installed the theme? For instance, did it take over 10 seconds to see the preview after you click “Update Preview?” If so, you will have to reset your blog. 
  • Is your theme up-to-date? If not, please update it!
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