Работает ваш скрипт нормально с несколькими select на странице, просто нужно обязательно задавать уникальное значение атрибута name:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
<style type="text/css">
span.select {
width: 229px;
height: 24px;
line-height: 21px;
font-family: Arial;
font-size: 12px;
background-image: url(../images/background_select.png);
background-color: #FFFFFF;
background-repeat: no-repeat;
overflow: hidden;
position: absolute;
margin-top: -2px;
margin-right: 0px;
margin-bottom: 0px;
margin-left: 0px;
}
#selectselect1 {
border: 1px solid #f00;
}
#selectselect2 {
border: 1px solid #0f0;
}
#selectselect3 {
border: 1px solid #00f;
}
</style>
<script type="text/javascript">
var checkboxHeight = "25";
var radioHeight = "25";
var selectWidth = "229";
document.write('<style type="text/css">input.styled { display: none; } select.styled { position: relative; width: ' + selectWidth + 'px; opacity: 0; filter: alpha(opacity=0); z-index: 5; }</style>');
var Custom = {
init: function() {
var inputs = document.getElementsByTagName("input"), span = Array(), textnode, option, active;
for(a = 0; a < inputs.length; a++) {
if((inputs[a].type == "checkbox" || inputs[a].type == "radio") && inputs[a].className == "styled") {
span[a] = document.createElement("span");
span[a].className = inputs[a].type;
if(inputs[a].checked == true) {
if(inputs[a].type == "checkbox") {
position = "0 -" + (checkboxHeight*2) + "px";
span[a].style.backgroundPosition = position;
} else {
position = "0 -" + (radioHeight*2) + "px";
span[a].style.backgroundPosition = position;
}
}
inputs[a].parentNode.insertBefore(span[a], inputs[a]);
inputs[a].onchange = Custom.clear;
span[a].onmousedown = Custom.pushed;
span[a].onmouseup = Custom.check;
document.onmouseup = Custom.clear;
}
}
inputs = document.getElementsByTagName("select");
for(a = 0; a < inputs.length; a++) {
if(inputs[a].className == "styled") {
option = inputs[a].getElementsByTagName("option");
active = option[0].childNodes[0].nodeValue;
textnode = document.createTextNode(active);
for(b = 0; b < option.length; b++) {
if(option[b].selected == true) {
textnode = document.createTextNode(option[b].childNodes[0].nodeValue);
}
}
span[a] = document.createElement("span");
span[a].className = "select";
span[a].id = "select" + inputs[a].name;
span[a].appendChild(textnode);
inputs[a].parentNode.insertBefore(span[a], inputs[a]);
inputs[a].onchange = Custom.choose;
}
}
},
pushed: function() {
element = this.nextSibling;
if(element.checked == true && element.type == "checkbox") {
this.style.backgroundPosition = "0 -" + checkboxHeight*3 + "px";
} else if(element.checked == true && element.type == "radio") {
this.style.backgroundPosition = "0 -" + radioHeight*3 + "px";
} else if(element.checked != true && element.type == "checkbox") {
this.style.backgroundPosition = "0 -" + checkboxHeight + "px";
} else {
this.style.backgroundPosition = "0 -" + radioHeight + "px";
}
},
check: function() {
element = this.nextSibling;
if(element.checked == true && element.type == "checkbox") {
this.style.backgroundPosition = "0 0";
element.checked = false;
} else {
if(element.type == "checkbox") {
this.style.backgroundPosition = "0 -" + checkboxHeight*2 + "px";
} else {
this.style.backgroundPosition = "0 -" + radioHeight*2 + "px";
group = this.nextSibling.name;
inputs = document.getElementsByTagName("input");
for(a = 0; a < inputs.length; a++) {
if(inputs[a].name == group && inputs[a] != this.nextSibling) {
inputs[a].previousSibling.style.backgroundPosition = "0 0";
}
}
}
element.checked = true;
}
},
clear: function() {
inputs = document.getElementsByTagName("input");
for(var b = 0; b < inputs.length; b++) {
if(inputs[b].type == "checkbox" && inputs[b].checked == true && inputs[b].className == "styled") {
inputs[b].previousSibling.style.backgroundPosition = "0 -" + checkboxHeight*2 + "px";
} else if(inputs[b].type == "checkbox" && inputs[b].className == "styled") {
inputs[b].previousSibling.style.backgroundPosition = "0 0";
} else if(inputs[b].type == "radio" && inputs[b].checked == true && inputs[b].className == "styled") {
inputs[b].previousSibling.style.backgroundPosition = "0 -" + radioHeight*2 + "px";
} else if(inputs[b].type == "radio" && inputs[b].className == "styled") {
inputs[b].previousSibling.style.backgroundPosition = "0 0";
}
}
},
choose: function() {
option = this.getElementsByTagName("option");
for(d = 0; d < option.length; d++) {
if(option[d].selected == true) {
document.getElementById("select" + this.name).childNodes[0].nodeValue = option[d].childNodes[0].nodeValue;
}
}
}
};
window.onload = function() {
Custom.init();
};
</script>
</head>
<body>
<div>
<form action="">
<fieldset>
<legend>Form Caption</legend>
<div>
<label for="select1">Select1:</label>
<select id="select1" name="select1" class="styled">
<option>option1</option>
<option>option2</option>
<option>option3</option>
</select>
</div>
<div>
<label for="select2">Select2:</label>
<select id="select2" name="select2" class="styled">
<option>option1</option>
<option>option2</option>
<option>option3</option>
</select>
</div>
<div>
<label for="select3">Select3:</label>
<select id="select3" name="select3" class="styled">
<option>option1</option>
<option>option2</option>
<option>option3</option>
</select>
</div>
</fieldset>
</form>
</div>
</body>
</html>