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Small, flashing gif banners that were popular on cites like geocities. Most of these are from old geocities sites, but some have been made recently in the same style. Most banner-type blinkies are 150x20px, but "blinkie" can describe many small flashing graphics of different sizes.
A style of graphic that's most popular on deviantart, an art website that was popular in the early 2000s. Usually around 99x56px.