In the 1980s manufacturers such as Hummel and Adidas began to design shirts with increasingly intricate designs, as new technology led to the introduction of such design elements as shadow prints and pinstripes. Hummel's distinctive halved strip designed for the Danish national team for the 1986 FIFA World Cup caused a stir in the media but FIFA worried about moiré artefacts in television pictures. Shorts became shorter than ever during the 1970s and 1980s, and often included the player's number on the front. In the 1991 FA Cup Final Tottenham Hotspur's players lined up in long baggy shorts. Although, the new look was derided, clubs in Britain and elsewhere had within a short time adopted the longer shorts. In the 1990s shirt designs became increasingly complex, with many teams sporting extremely gaudy colour schemes. Design decisions were increasingly driven by the need for the shirt to look good when worn by fans as a fashion item, but many designs from this era have since come to be regarded as amongst the worst of all time. In 1996, Manchester United notoriously introduced a grey strip which had been specifically designed to look good when worn with jeans, but abandoned it halfway through a match after manager Alex Ferguson claimed that the reason why his team was losing 3–0 was that the players could not see each other on the pitch. United switched to different colours for the second half and scored one goal without reply. The leading leagues also introduced squad numbers, whereby each player is allocated a specific number for the duration of a season. A brief fad arose for players celebrating goals by lifting or completely removing their shirts to reveal political, religious or personal slogans printed on undershirts. This led to a ruling from the International Football Association Board in 2002 that undershirts must not contain slogans or logos; since 2004 it has been a bookable offence for players to remove their shirts.