See http://pueblosdelsur.wordpress.com under mistylook theme.
One of the top tabs is hidden by the Search box.
There are two solutions:
1. make the search box shorter (don’t know if it is possible without working in the CSS)
2. shorten the name of the home tab (in Spanish, it could be “Inicio” instead of “Página principal”
As for the second solution, which seems to be easier, I do not find the way to do that.