Fear of Friday the 13th may be the biggest superstition of all time. There are many reasons why 13 is considered an unlucky number, and some say Friday is a bad day because that's when the Crucifixion took place. It also used to be the day for hangings. No one is exactly sure how fear of the combined date took root.
It's been suggested that 13 is an unlucky number because it is one more than a perfect dozen - Judas' appearance at the Last Supper, making 13 men, is often cited. So strong is the superstition that some hotels skip 13 when naming floors. There is even a name for fear of the number: Triskedekaphobia.
It's a common superstition not to open an umbrella indoors, although its origin is unclear. It's been said that doing so might be an insult to the sun, or to the spirits already protecting you at home.
It may be unlucky (and it's definitely dirty) to place your shoes on a table. Various legends hold this will bring a day's bad luck, a quarrel with a mate and even death. It's also been said that you can undo this curse by putting the shoes on the floor again before putting them on.
Itching or buzzing in the left ear is said to mean you are being badmouthed, or will face bad luck. On the right side, you are being praised or will see good fortune. The left side of the body is considered to be bad, even devilish, in the folklore of many cultures.
It's easy to recover if you commit the supposedly unlucky act of spilling salt: just throw a pinch at the devil over your left shoulder, the legend goes. This belief most likely dates back to when salt was a scare commodity.
Walking under a ladder
The shape of a ladder against a wall makes a triangle, an allusion to the Christian holy trinity, and also looks like gallows. Years ago, people thought walking through the former was blasphemous, and the latter tempted fate. These days, it's still discouraged, if only because you might get something spilled on your head.
The belief that it's bad luck -- sometimes even a sign of imminent death -- to toss a hat on a bed most likely traces back to when people had poor hygiene, and the hat might have spread lice to the mattress.
For every portent of bad luck, there's something that means good things. Groundhog Day, based on a German superstition that if a hibernating animal casts a shadow on Feb. 2 winter will drag on, and if it doesn't, spring will come early, can go either way.
Both a warning of bad luck and bit of fun for kids, most people have heard the rhyme, "Step on the crack, break your mother's back."
In ancient times, it was thought that mirrors contained the soul of the gazer. From this comes the belief that seven years of bad luck will strike you if you break one.
Hide the bride
Even people who are not particularly superstitious follow the belief that the bride should not see the groom before reaching the altar. An obvious reason is that it might give him second thoughts; some say it's because the bride is in a transitional period and is therefore bad luck for others.
There are numerous rules a bride is supposed to follow on her wedding day, and just about anything can be seen as bad luck. Another thought is that she should be the first to cut the cake, otherwise there will be no children. When the couple slices it together, it's said to signify their commitment to share.
"Don't let a black cat cross your path," the saying goes. Not only are they supposedly a sign of bad luck, but in folklore black cats can be witches in disguise. But sometimes, such as on wedding days, they are actually considered a good sign.