Hi,
the problem is that you used the "RightArrow". What you want to use is \[Rule].
Plot[Tan[x], {x, 0, 10}, PlotRange -> Automatic]
or
Plot[Tan[x],{x,0,10}, PlotRange \[Rule] Automatic]
should both work. The think is that the typesetting of \[Rule] and \[RightArrow], i.e. how they are displayed, is the same.
Cheers,
Marco
