Change
<style>
.col {display: inline;}
.leftcolumn{ float: left; width: 15%; }
.rightcolumn{ float: right; width: 15%; }
.maincol{ display: inline-block; width: 70%; }
</style>
to
<style>
.col {display: inline-block;}
.leftcolumn{ float: left; width: 15%; }
.rightcolumn{ float: right; width: 15%; }
.maincol{ float: left; width: 70%; }
</style>