Microsoft Internet Explorer contains a bug which means that it is very liberal in its interpretation of hexadecimal values in colors. Missing digits are treated as 0 also. An incorrect digit is simply interpreted as 0. For example the values #F0F0F0, F0F0F0, F0F0F, #FxFxFx and FxFxFx are all the same. This can be used to refresh tricks like Invisible Ink and Camouflage.