.test3 span {
position: relative;
}
.test3 span a {
position: relative;
z-index: 2;
}
.test3 span a:hover, .test3 span a:active {
z-index: 4;
}
.test3 span input {
background: transparent;
border: 0;
cursor: pointer;
position: absolute;
top: -1px;
left: 0;
width: 101%; /* Hacky */
height: 301%; /* Hacky */
z-index: 3;
}
.test3 span input:focus {
background: transparent;
border: 0;
z-index: 1;
}

<div class="test3">
<span><input type="text" value="&nbsp;" readonly="true" />
<a href="http://www.baidu.com">Double click me</a></span>
</div>