No, this is not an excel error, it has to do with how all computers handle the floating point situation. If you google it, you will get a bunch of hits, here is the text from just 1 of tghem...
The most common situation is illustrated by the decimal number 0.1. Although it has a finite decimal representation, in binary it has an infinite repeating representation. Thus when = 2, the number 0.1 lies strictly between two floating-point numbers and is exactly representable by neither of them.