How does Privoxy know what is an ad, and what is not?
490 491 Privoxy’s approach to blocking ads is twofold: 492 493 First, there are certain patterns in the locations (URLs) of banner 494 images. This applies to both the path (you wouldn’t guess how many web 495 sites serve their banners from a directory called “banners”!) and the host 496 (blocking the big banner hosting services like doublecklick.net already 497 helps a lot). Privoxy takes advantage of this fact by using URL patterns 498 to sort out and block the requests for things that sound like they would 499 be ads or banners. 500 501 Second, banners tend to come in certain sizes. But you can’t tell the size 502 of an image by its URL without downloading it, and if you do, it’s too 503 late to save bandwidth. Therefore, Privoxy also inspects the HTML sources 504 of web pages while they are loaded, and replaces references to images with 505 standard banner sizes by dummy references, so that your browser doesn’t 506 request them anymore in the first place. 507 508 Both of this invol
