Salut,
Ton effet est possible en full css3 grâce a un background dégradé: Grandient Generator
Compatible Opera, Firefox, Chrome, IE10 et IE9 a moitié (f***ing IE).
Si c'est un effet de "relief" que tu veut faire il faut que tu mette un fond uni a ta div et que tu rajoute une div par dessus (ou va voir du coté de :before :after) de la même taille que t'a div avec un font dégradé en parti transparent dans ce style :
/* IE9 SVG, needs conditional override of 'filter' to 'none' */
background: url(data:image/svg+xml;base64,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);
background: -moz-linear-gradient(-45deg, rgba(0,0,0,0.21) 0%, rgba(0,0,0,0.15) 50%, rgba(0,0,0,0.42) 51%, rgba(0,0,0,0.16) 56%, rgba(0,0,0,0.22) 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, right bottom, color-stop(0%,rgba(0,0,0,0.21)), color-stop(50%,rgba(0,0,0,0.15)), color-stop(51%,rgba(0,0,0,0.42)), color-stop(56%,rgba(0,0,0,0.16)), color-stop(100%,rgba(0,0,0,0.22))); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(-45deg, rgba(0,0,0,0.21) 0%,rgba(0,0,0,0.15) 50%,rgba(0,0,0,0.42) 51%,rgba(0,0,0,0.16) 56%,rgba(0,0,0,0.22) 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(-45deg, rgba(0,0,0,0.21) 0%,rgba(0,0,0,0.15) 50%,rgba(0,0,0,0.42) 51%,rgba(0,0,0,0.16) 56%,rgba(0,0,0,0.22) 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(-45deg, rgba(0,0,0,0.21) 0%,rgba(0,0,0,0.15) 50%,rgba(0,0,0,0.42) 51%,rgba(0,0,0,0.16) 56%,rgba(0,0,0,0.22) 100%); /* IE10+ */
background: linear-gradient(135deg, rgba(0,0,0,0.21) 0%,rgba(0,0,0,0.15) 50%,rgba(0,0,0,0.42) 51%,rgba(0,0,0,0.16) 56%,rgba(0,0,0,0.22) 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#36000000', endColorstr='#38000000',GradientType=1 ); /* IE6-8 fallback on horizontal gradient */
Cordialement,
TWIK.