array.indexOf does not work in IE8

[pdc]

Webpage error details

User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; WOW64; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E; MS-RTC LM 8)
Timestamp: Thu, 17 May 2012 11:03:02 UTC

Message: Object doesn't support this property or method
Line: 73
Char: 13
Code: 0
URI: http://static.kanbo.me.uk/js/board.js

Message: Object doesn't support this property or method
Line: 73
Char: 13
Code: 0
URI: http://static.kanbo.me.uk/js/board.js

Message: Object doesn't support this property or method
Line: 73
Char: 13
Code: 0
URI: http://static.kanbo.me.uk/js/board.js

-----8<-----cut here-----8<-----

The propery or method in question is Array.indexOf. See

http://soledadpenades.com/2007/05/17/arrayindexof-in-internet-explorer/

[pdc]

Rejigged the JavaScript code to avoid using indexOf