L'Hopital's rule says that if g and f both have limit 0 as a goes to a, then
[tex]lim_{x\rightarrow a}\frac{f(x)}{g(x)}= \frac{lim_{x\rightarrow a}f(x)}{lim_{x\rightarrow a}g(x)}[/tex]
Since, in this problem, the limit of the numerator, [itex]lim_{x\rightarrow 0}x-1[/itex] is -1, not 0, LHopital's rule does not apply.
As x approaches 0, the numerator stays around -1 while the denominator goes to 0: the fraction goes toward [itex]-\infty[/itex].
Some people would say "the limit does not exist". Others would say the limit is [itex]-\infty[/itex] which is just a way of saying the limit does not exist in a particular way.