Hi, just bought a secondhand Macbook Pro from eBay and just have a question about the screen. There is a very small 'dot' on the screen (about the size of an old-school CRT pixel) which appears white when the screen is off and black when the screen is white. It is also slightly raised so I can feel it very faintly when I run my finger tip across it. The screen was filthy when it arrived and there were similar marks on the screen but these seem to have come off with screen cleaner and a microfibre cloth however this one remains. Is this a chip? I had assumed a chip would be concave but this is definitely raised... Any ideas?