Oh my god. I found the solution!! but strange that the component .center-block in boostrap.css doenst work for safari. I just added this in my site.css:
.middle {
display: inline-block;
margin-right:0 auto;
margin-left:0 auto;
margin: 0 auto;
width: 200px;
float: none !important;
display: block;
}
And it seems that it works now for all browers.