Лавсановые Волокна, как вариант...
<!DOCTYPE html>
<html>
<head>
<style>
</style>
<script>
function Set() {
var o=document.getElementById('form1').getElementsByTagName('select')
var i
for (i=0; i<o.length; i++) {
o[i].selectedIndex=1
}
}
</script>
</head>
<body>
<form id="form1" name="form1" method="post" action="">
<select name="myselectid" id="myselectid">
<option value="first">first </option>
<option value="second">second</option>
<option value="third">third</option>
</select>
<select name="myselectid" id="myselectid">
<option value="first">first </option>
<option value="second">second</option>
<option value="third">third</option>
</select>
<select name="myselectid" id="myselectid">
<option value="first">first </option>
<option value="second">second</option>
<option value="third">third</option>
</select>
<br />
<br />
<input type='button' value='Set' onclick='Set()' />
</form>
</body>
</html>