<style>
.float { position:fixed; width:60px; height:60px; top:15px; right:15px; background-color:#ff3300; color:#FFF; border-radius:50px; text-align:center; font-size:30px; box-shadow: 2px 2px 3px #999; z-index:100; } .my-float{ margin-top:16px; color: white; }
</style>

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min....
<a href="https://wa.me/525591956389/?text=Hola%2C%20estoy%20interesado%20en%20cre... class="float" target="_blank">
<i class="fa fa-whatsapp my-float"></i>
</a>

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