One of most interesting things when blocking third-party content on websites by default, is how web developers handle that. The best example might be captchas.
First, I almost never notice that they're missing. Because they're just embedded without any hint that they exist (e.g. a frame or just „Captcha:“). Second, it's interesting to see what happens when proceeding. Some sites are pretty clear („Captcha hasn't been solved“), some just give you a generic error, some just won't proceed at all.
@esureL Ugh, right? Watching websites degrade disgracefully is usually a dumpster fire. OTOH I'm always impressed when I visit a site and it loads mostly functional despite only having having access to 1st-party CSS and images.