[Deff]

<style id="a1">
#text0 {
opacity:0.1;
}

#text1 {
opacity:0.2;
}

#text3 {
opacity:0.3;
}
</style>
</style>

<script type="text/javascript">
  var v=document.getElementById('a1')
  var str=v.innerHTML;
  var t3=str.replace(/[\s\S]*?#text3 \{([\s\S]*?)\}[\s\S]*$/gim,'$1')
  alert(t3)
</script>