Установить определенный размер CSS кнопки?
Замените

.button {...}

на

.button {
   width: 250px;
   height: 26px;
   border: 1px solid #0a3c59;
   background: #3e779d;
   background: -webkit-gradient(linear, left top, left bottom, from(#65a9d7), to(#3e779d));
   background: -webkit-linear-gradient(top, #65a9d7, #3e779d);
   background: -moz-linear-gradient(top, #65a9d7, #3e779d);
   background: -ms-linear-gradient(top, #65a9d7, #3e779d);
   background: -o-linear-gradient(top, #65a9d7, #3e779d);
   background-image: -ms-linear-gradient(top, #65a9d7 0%, #3e779d 100%);
   /*padding: 12px 24px;*/
   -webkit-border-radius: 6px;
   -moz-border-radius: 6px;
   border-radius: 6px;
   -webkit-box-shadow: rgba(255,255,255,0.4) 0 1px 0, inset rgba(255,255,255,0.4) 0 1px 0;
   -moz-box-shadow: rgba(255,255,255,0.4) 0 1px 0, inset rgba(255,255,255,0.4) 0 1px 0;
   box-shadow: rgba(255,255,255,0.4) 0 1px 0, inset rgba(255,255,255,0.4) 0 1px 0;
   text-shadow: #7ea4bd 0 1px 0;
   color: #eff1f2;
   font-size: 17px;
   font-family: helvetica, serif;
   text-decoration: none;
   vertical-align: middle;
   }

width: ...; + text-align: center; ? Или в чем подвох здесь?