Ecco il Codice che m'interessa modificare:
#sidebar-first,
#sidebar-second {
/*width: 240px;*/
/* Larghezza Colonna a Sx e Dx*/
width: 15%;
}


Qui sotto il codice completo:


/* ---------- Basic Layout Styles ----------- */


html,
body,
#page {
height: 100%;
/*width: 90%;*/
}
#page-wrapper {
/*min-width: 960px;*/
/*min-width: 90%;*/
}
#header div.section,
#featured div.section,
#messages div.section,
#main,
#triptych,
#footer-columns,
#footer {
/*Larghezza della Pagina in Assoluto*/
width: 90%;
margin-left: auto;
margin-right: auto;
}
#header div.section {
position: relative;
}
.region-header {
float: right; /* LTR */
margin: 0 5px 10px;
}
.with-secondary-menu .region-header {
margin-top: 3em;
}
.without-secondary-menu .region-header {
margin-top: 15px;
}
#secondary-menu {
position: absolute;
right: 0; /* LTR */
top: 0;
/*width: 480px;*/
/* Secondary Menu è quello in alto a dx dove c'è LogOut*/
width: 20%;
}
#content,
#sidebar-first,
#sidebar-second,
.region-triptych-first,
.region-triptych-middle,
.region-triptych-last,
.region-footer-firstcolumn,
.region-footer-secondcolumn,
.region-footer-thirdcolumn,
.region-footer-fourthcolumn {
display: inline;
float: left; /* LTR */
position: relative;
}
.one-sidebar #content {
/*width: 720px;*/
width: 84%;
}
.two-sidebars #content {
/*width: 480px;*/
width: 69%;
}
.no-sidebars #content {
/*width: 100%;*/
float: none;
}
#sidebar-first,
#sidebar-second {
/*width: 240px;*/
/* Larghezza Colonna a Sx e Dx*/
width: 15%;
}
#main-wrapper {
/*min-height: 300px;*/
min-height: 30%;
}
#content .section,
.sidebar .section {
padding: 0 15px;
}
#breadcrumb {
margin: 0 15px;
}
.region-triptych-first,
.region-triptych-middle,
.region-triptych-last {
margin: 20px 20px 30px;
width: 280px;
}
#footer-wrapper {
padding: 35px 5px 30px;
}
.region-footer-firstcolumn,
.region-footer-secondcolumn,
.region-footer-thirdcolumn,
.region-footer-fourthcolumn {
padding: 0 10px;
/*width: 220px;*/
width: 25%;
}
#footer {
/* width: 940px;*/
/*min-width: 920px;*/
min-width: 90%;
}