GFork

Runs on Firefox and on Google Chrome browsers.

After installing this script clicking on any advert/image etc., whilst holding down the "Ctrl" key, erases it. Upon revisiting the page at another time, the advert/image etc. will still be erased. A simple Click on an erased (curtained) space temporarily reveals that which was erased.

The script also adds to the GM menu a command that gives access to the the scripts options. One of which allow one to set the 'curtain' image to a http image address or a base64 string. It also allows manual alteration of the selectors used to find elements for erasure. Another options allows for complete erasure of items leaving more space for other items on the page (for this, untick the "preserve layout" tickbox).

See this option menu under the browser's Tools menu --> GreaseMonkey-->UserScriptCommands...-->EraseWebElements.

There is no GM menu on Chrome browser, so to access the menu command, ctrl-click
anywhere then click on link (Erase Web Elements) that appears in the popup, then use the menu then when closed hit escape to close original popup.