There is a usability problem when you visit a site on which ads are being served. The top banner ad doesn't render immediately, and then when it does, it causes the rest of the page below it to jump down by just about the amount that e.g. attempting to click on the downvote arrow ends up clicking on the upvote arrow.
This is easy to fix if you notice, but if you were planning to click somewhere else, you will miss by rather a large distance. This is annoying and hardly serves any useful purpose, and in the worst case could lead to you clicking on something you really didn't want to click.
I don't know enough about the underlying technology to propose a fix, but a thing which used to work already in the 1990s was to reserve space for an image if you could tell in advance how large it was going to be. Banner ads typically have this property, and so I'm imagining this should be possible. Examining the page source reveals an
iframe element with
height="0" attributes which seems like precisely the wrong thing here, but like I said, I probably don't understand this well enough.
Frustratingly, the image block my browser offers doesn't help at all; the jump happens even if the image is not displayed (at least in Chrome on Mac).
The particular use case for me is to flag obvious spam quickly; I basically never do anything else on the Drupal site, for example, and so probably will never earn enough rep there to not see the ads. When spam is dead obvious, you really want to be able to just flag it and move on.