[OSM-newbies] visualization of a street direction

[guille]

When using different zoom, a particular street changes its direction
(I mean the arrow symbol). It's tagged with oneway=yes.
http://www.openstreetmap.org/?lat=39.468268&lon=-0.357743&zoom=18

The name of the street is Calle Santa Rosa (the straight line). I
certainly know that the direction of that street is from east to west.

What can be the problem?

Remember that I'm a newbie, so the answer could be obvious :)