Yo, I -think- I have just figured out how to remove the new Yahoo gemini dashboard ads tumblr has started pushing on us with Adblocker Plus.
Click on the Adblocker Plus menu, and go to “Filter Preferences”.
This brings up a box with “Add Filter” in the top right corner. Click that and type in:
Which should hide the entire ad that Yahoo said they weren’t going to put into the site a couple of years ago but totally decided to put in after they thought everyone forgot they said that.
(Please note that I’ve only tested this in Firefox, and it appears to work in Opera too, but your mileage may vary as tumblr tweak their code to keep up with adblocking software.)