To be able to do that, it would likely require hours, maybe more, of coding, but if done correctly (I don't fully know code, but I know enough to get around), then there might be a Javascript listener that only activates when the user goes into the "login" dialouge box, and if they sign in, it auto-refreshes the page, or sets the visibility of the ad to invisible.
If I could help, I would, but I am just a random person. I in no way have any direct contact to or relations with the perchance devs. I am simply someone who's seen perchance since close to the beginning, and I've been using perchance to teach myself html, Javascript, and CSS.
So no, I cannot add these into perchance myself, however if one of the mods reads this, perchance they might take the idea into consideration as a future update. :D