What is a glitch?  This term is used mostly in the computer and electronic industries.  The term is also used among video game players.  The term originated from the German glitsching, meaning ("slippery" or "to slip") and the Yiddish word gletshn, or "to slide or skid." This is a fairly new word , on July 23, 1965, Time magazine used it in an article to define "Glitches - a spaceman's word for irritating disturbances."

In the electronic industry a glitch is a short duration of an electronic pulse that usually is a fault or design error.  A computer glitch is a system failure.  In the video game world, a glitch is a programming error.  There are actually game testers that will play a video game just to locate any glitches that might be in a game.
On the other hand, there are video game players that will exploit a glitch to advance in any given game which is called "Glitching."  

As the web world grows, so do glitches.  In this day and age of the web maniac glitches can cause major damage and cause companies thousand of dollars.  Apparently this past holiday season, Yahoo's system "Yahoo Merchant Solutions" went down for 14 hours, along with thousands of e-commerce companies on one of the busiest times of the year.  

The causes of these kind of problems range from system upgrades, human error or just electrical failures.  As frustrating and costly as this may be glitches are more part of internet the bigger it gets.