If anyone wants to take a look I have now added encrypting of spaces in the algorithm and it still changes the letters nicely because I added my own word-wrap to the textbox, so that when the spaces are turned into other characters the browsers don't move the text up and down lines. Also the key can be 50 characters in length now.
[URL="http://www.seabreezecomputers.com/encrypter/"]http://www.seabreezecomputers.com/encrypter/[/URL]