1) Reproduce error: Write 1 in cell A1. Write 0,9 in cell A2. Select two previously filled cells, hover the cursor over the cell's lower right corner and drag down. 2) Error: In cell where should be zero, will be value other than zero (here 2,22044604925031E-016).
I think you can find an accurate explanation here: http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems
Yes this has been reported a lot of times and all of our expert developers say it's not a bug. Closing as NOTABUG
*** Bug 68448 has been marked as a duplicate of this bug. ***
*** Bug 91342 has been marked as a duplicate of this bug. ***
Created attachment 166198 [details] a sample of better results, see comments in sheet something is changed, in ver 7.1 '0' displays '0', but other values have small inaccuracies ... as mathematically incorrect and as better results are! possible - see attachement - i'd say bug.