javascript + select tags

[tasox]

hello everybody!!
if you have many select tags how i can find the selections form every select tag??please in javascript code!!

i wrote this but it's wrong because this code gives me the values from the first select tag

function getoptionvalues() {
var t="select30";
for(var i=0;i<document.getElementById(t).length;i++){
var x=document.getElementById(t)[i].value;
alert(x); } }

for example

<select id="select30">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</select>

<select id="select30">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</select>

<select id="select30">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</select>

<select id="select30">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="mercedes">Mercedes</option>
<option value="audi">Audi</option>
</select>

[tasox]

these days i read and learn more about my problem!so forget my previous post because is wrong
the code is here:

<div align="right" id="parent" name="parent">
<select name="select30" id="select30" value=""/>here inside i have options values and work dynamically with query to my DB</select>
<input type="button" id="moreFields" value="+" onclick=""/> //add select tags
<input type="button" value="-" onclick="" /> //remove select tags
<div name="child" id="writeclone"></div> //here cloned the  child from parent DIV 
</div>
<input type="button" name="enter" id="" value="ENTER" onclick="getoptionvalues();"/> 

My problem is how i can get the names or id's from child DIV when + button fired.When this button fired create child DIVs in Child DIV!!Can anybody HELP ME to correct my JAVASCRIPT code

<script> function getoptionvalues() {
var parent=document.getElementById('parent');
for (var count=0;count<parent.childNodes.length;count++) {
if(parent.childNodes[count].tagName =='DIV') {
alert ('parent.childNodes[count]');
}

}

} </script>