It seems as if every team in sports has some sort of "curse", and the Vikings are no different. In fact, there curse has been compared to the curse of the Billy Goat Chicago Cubs fans have endured for years.
The curse explanation goes like this as explained on purplepride.org:
The Vikings, even though they are a very successful franchise, are faced with championship futility, much like the Chicago Cubs, the Toronto Maple Leafs and many other successful franchises in other sports. Many attribute their futilities to "curses", such as the Cubs' Billy Goat curse. The Vikings have the more esoteric runestone curse, named for the Kensington Runestone, claimed to be Viking in origin, which was found near Alexandria, Minnesota. Legend has it that the runestone predicts the fate of the Minnesota Vikings in the future.
22 Norwegians on
discovery voyage from
Vinland over (the) west we
had camp by 2 skerries one
days journey north from this stone
we were and fishe(ed) one day after
we came home found 10 men red
with blood and dead.
The 22 Norwegians in this reference are a reference to the 22 players that play on a starting offense and defense on an NFL football team. The 10 dead are usually a reference to a massive group of injuries of an offense or defense.
A curse is a nostalgic part of sports, but this is simply not true.
The text is taken from the Kensington Runestone found in Solem, Minnesota in 1898. nearly every runeologists that ever examined the piece, completely believe the stone is a hoax, and nothing more.