How was Pixel Perfect tested — pixel-by-pixel or approximately?

Pixel Perfect checking usually does not mean an exact match of every pixel, but rather a very close correspondence to the design. In practice, key interface elements — such as margins, sizes, colors, fonts — are checked to visually match the layout. Sometimes tools are used that overlay the layout on the page with transparency to see discrepancies. Absolute pixel-to-pixel matching is rarely achievable due to browser rendering features and different screens, so visual accuracy and conformity to the design are most important.