There were probably hundreds of articles on this and were extremely lengthy, here's one a bit shorter. Don’t know if it's true or not but when you think about it, it's pagan and doesn’t really matter, interesting though. It came from a website called Town Time written by Steven Wilcox. This is only a few paragraphs, that way some may have the time to read it. (if you can bare it!);
Not only is it a very old superstition, but experts say that Friday the 13th as a day of bad luck is the most widespread superstition in the United States. Because this Friday happens to be the 13th, you can expect less people will get out of bed and follow their normal routines- seriously. In fact, it’s not just those with paraskevidekatriaphobia who suffer, Friday the 13th means bad news for the economy. A report from National Geographic News estimated that $800 to $900 million is lost in business on this day, as people avoid flying, driving, eating in restaurants, going to work and even getting married.
But despite all of the hoopla, there is no written evidence for Friday the 13th, folklorists say, but several theories have been proposed about the origin of the superstition. One theory says that it is a modern combination of two older superstitions: that 13 is an unlucky number and that Friday is an unlucky day. Well, if you’re inclined to be a worrier or pessimist, there are probably countless testimonies to this claim, but here are some that have passed through history.
Some say the reputation of the number 13 goes back to ancient Norse culture and mythology when the beloved hero Balder was killed at a banquet by the god Loki, who crashed the party of 12, bringing the group to 13. Along with the Last Supper, this story led to one of the most deeply-rooted 13-related beliefs that you should never sit down to a meal in a group of 13, or one will die within the year.
Other traditions say that on Friday the 13th in 1306, King Philip of France arrested the reverend Nights Templar and tortured them, making the occasion as a day of evil, but this claim is said to be a modern-day invention. In British tradition, Friday was the day for public hangings and there were supposedly 13 steps leading up to the noose. Even Chaucer referred to Friday as a day of bad luck in the Canterbury Tales, which was during the medieval times of the 14th century.
Just another day as far as I'm concerned, no different to any other.