cf http://wordpress.org/support/topic/twenty-fourteen-theme-not-full-width-for-high-resolution-monitors
et ajouter le css:
.site,
.site-header {
max-width: 100%;
}
.site-content .entry-header,
.site-content .entry-content,
.site-content .entry-summary,
.site-content .entry-meta, .page-content {
/* Original max-width: 474px */
max-width: 90%;
margin-right: 10px;
}
.hentry {
max-width: 100%;
}
