How to Hide Tumblr Theme Creditsby Chad Davis
Remove unwanted text such as theme credits from your blog by editing your theme's HTML code. While many themes request that keep credits for the developer of the theme, you can remove the credits by deleting the text in Tumblr's HTML editor. The HTML editor can be found on Tumblr's Customize page.
Remove Theme Credits
Log in to the Tumblr website. Click on the "Customize" button on the right sidebar of your Tumblr Dashboard. Click the "Edit HTML" link to open the HTML code for your current theme. Locate the text you'd like to remove form your blog. For example, press "Ctrl-F" and then enter "Theme by" into the Search For field. Delete the surrounding code beginning with the opening <div tag and ending with the closing </div> tag. Click "Update Preview" and then click "Save" to finish making changes.