If you pass parseInt a number with a zero in front of it, such as “020″, without specifying a radix, you may get funny results…

parseInt("020");	// Result: 16

This is because when the input string begins with “0″, parseInt assumes the radix is 8 (octal), and converts the string to an octal number. Perhaps it’s just me, but I don’t usually work in octals!

You can avoid this problem by supplying it with the radix that you want to use.

parseInt("020", 10);	// Result: 20

For more information, I recommend that you read the parseInt page at the Mozilla Developer Centre.