http://www.loremipsum.net/about.html

What is 'lorem ipsum'?
'Lorem ipsum' is simply dummy text of the printing and typesetting industry. It has been the industry's standard dummy text ever since the 1500s. It has been popularised 'recently' with desktop publishing software and in the 1960s with the release of Letraset sheets containing 'lorem ipsum' passages.

Roots of 'lorem ipsum'?
'Lorem ipsum' is not simply random text. It is actually over 2000 years old and it has roots in a piece of classical Latin literature from 45 BC. 'Lorem ipsum' comes from sections 1.10.32 and 1.10.33 of "de Finibus Bonorum et Malorum" (The Extremes of Good and Evil) written in 45 BC by Marcus Tullius Cicero. The first line of 'lorem ipsum', "Lorem ipsum dolor sit amet...", can be read out of a line from section 1.10.32. This book was very popular during the Renaissance and it is a treatise on the theory of ethics.

Well, why to use 'lorem ipsum'?
It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using 'lorem ipsum' is that it has a more-or-less normal distribution of letters, as opposed to using 'This here is content' or 'Osama Bin Laden wanted dead or alive', making it look like readable text and there also has been many examples what has happened if someone has forgotten to change the dummy text for the final copywrite text.
   In Finland there was couple of years ago this one bookshop banner in public internet with 'Buying a book is as easy as hitting a child' text in it.