<a class="a-btn" href="#">
<span class="a-btn-text">Un bot&oacute;n</span>
<span class="a-btn-slide-text">animado</span>
<span class="a-btn-icon-right">&nbsp;</span> </a>

<style><!--
/* el enlace es el contenedor */
.a-btn {
background:#CDE;
background:-moz-linear-gradient(#CDE, #678);
background:-webkit-linear-gradient(#CDE, #678);
background:-o-linear-gradient(#CDE, #678);
background:-ms-linear-gradient(#CDE, #678);
background:-linear-gradient(#CDE, #678);
filter:progid:DXImageTransform.Microsoft.gradient( startColorstr='#CDE', endColorstr='#678',GradientType=0 );
border:1px solid #89A;
border-radius:20px;
box-shadow:0px 1px 1px rgba(255,255,255,0.8) inset, 1px 1px 3px rgba(0,0,0,0.2), 0px 0px 0px 4px rgba(188,188,188,0.5);
display:inline-block;
height:40px;
line-height: 40px;
margin:10px 0px;
padding: 0 70px 0 20px; /* esto dependerá del tamaño de la imagen */
position:relative;
-webkit-transition:all 0.3s linear;
-moz-transition:all 0.3s linear;
-o-transition:all 0.3s linear;
-ms-transition:all 0.3s linear;
transition:all 0.3s linear;
}
/* el texto visible */
.a-btn-text {
color:#456;
display:block;
font-size:20px;
text-shadow:0 1px 1px #FFF;
white-space:nowrap;
-moz-transition:all 0.2s linear;
-webkit-transition:all 0.2s linear;
-o-transition:all 0.2s linear;
-ms-transition:all 0.2s linear;
transition:all 0.2s linear;
}
/* el texto oculto */
.a-btn-slide-text {

background:#456; color:#FFF;
font-size:20px;
font-family: Georgia;
height:100%;
line-height:40px;
overflow:hidden;
position:absolute;
right:52px;
text-align:left;
text-indent:10px;
text-shadow:1px 1px 1px #000;
top:0px;
white-space:nowrap;
width:0;
-moz-transition:width 0.3s linear;
-webkit-transition:width 0.3s linear;
-o-transition:width 0.3s linear;
-ms-transition:width 0.3s linear;
transition:width 0.3s linear;
}
/* el contenedor de la imagen derecha */
.a-btn-icon-right {
border-left:1px solid #89A;
box-shadow:1px 0px 1px rgba(255,255,255,0.4) inset;
height:100%;
position:absolute;
right:0;
top:0;
width:52px;
}
/* y la imagen */
.a-btn-icon-right span {
background:transparent url(arrow_right.png) no-repeat 50% 55%;
height:38px;
left:50%;
margin:-20px 0px 0px -20px;
opacity:0.7;
position:absolute;
top:50%;
width:38px;
-moz-transition:all 0.3s linear;
-webkit-transition:all 0.3s linear;
-o-transition:all 0.3s linear;

-ms-transition:all 0.3s linear;
transition:all 0.3s linear;
}
/* los efectos hover */ .a-btn:hover {
padding-right:180px;
}
.a-btn:hover .a-btn-text {
color:#000;
text-shadow:0px 1px 1px #000;
}
.a-btn:hover .a-btn-slide-text {
width:100px;
}
.a-btn:hover .a-btn-icon-right span {
opacity:1;
}.a-btn:hover {}
.a-btn:hover .a-btn-slide-text {}
--></style>