IE shit and CSS

Here's a quick one, I don't know whether it's my fault or Redmond people's fault.
Simply, I decided to try foolab under IE, And what the hell, The mission statement block had borders and a background color, I had to explicitly tell IE not to add a border and not to use a background color.
Now the killer thing was

that the blocks are not displayed correctly, After trying to figure out why, I realised that IE IGNORED the comments starting with "//" in the CSS, Now someone tell me why the shit is this happening ?
So I had to erase the line: "// width: 100%;" though it's a comment!