@AlbertVilella: Please delete your custom css and add the following css. Your css is only for fixed with. When you change the width, you need to change the width as per the screen size.
@media screen and (min-width: 783px) {
.two-columns #primary { width: 900px; }
.two-columns #secondary { width: 242px; }
}
@media screen and (max-width: 1280px) {
.two-columns #primary { width: 830px; }
}
@media screen and (max-width: 1152px) {
.two-columns #primary { width: 770px; }
}
@media screen and (max-width: 1100px) {
.two-columns #primary { width: 690px; }
}
@media screen and (max-width: 1000px) {
.two-columns #primary { width: 630px; }
}
@media screen and (max-width: 940px) {
.two-columns #primary { width: 480px; }
}
@media screen and (max-width: 782px) {
.two-columns #primary { width: 100%; }
}
.
