CSS

How to write something inside image

//HTML code
<div class="relative">
      <img src="" width="100%"/>                                                            
      <span class="caption">some thing</span>
</div>

//CSS code
.relative {
    position: relative;
}
.relative .caption {
    position: absolute;
    bottom: 0;
    width: 100%;
    padding: 10px;
    left: 0;
    background: rgba(0,0,0,0.7);
}