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% replaces any number of letters (la% - lake, lamp)_ replaces one letter (ca_ - car, cat)

Crossword clues for They pop up on web pages 3 letters:

ADS: Web page "pop-ups"
ADS: Web page "pop-ups," e.g.
ADS: They pop up on web pages
ADSITE: Web page full of pop-ups
ADSITE: Web page that's nothing but pop-ups