twenty twelve not showing well in chrome

I do not understand why my blog http://www.sinapsi.org shows up well in Firefox and Internet Explorer and Edge and Safari, but in Chrome Version 47.0.2526.106 m has the header narrow.

I’m using twenty twelve theme with only this minor mod at line 1466 of style.css I changed max-width in order to properly show adsense:

.site {
margin: 0 auto;
max-width: 960px;
max-width: 68.571428571rem;
overflow: hidden;

to:

.site {
margin: 0 auto;
max-width: 960px;
max-width: 74.571428571rem;
overflow: hidden;