如何在搜索引擎上提交时删除URL参数

I built my own search engine at my website.

I want the output of my search at URL when I click Submit (as Search Button) is :

http://inindonesia.org/marketplace/tags/oleh-oleh-khas-medan

But, When I click Submit (search button), the output is :

http://inindonesia.org/marketplace/tags/?search=oleh+oleh+khas+medan&hidden=oleh-oleh-khas-medan&Submit=Cari+Produk

My code is :

<form autocomplete="off" action="/marketplace/tags/(i want this get parameter from the value input id "hidden", example : oleh-oleh-khas-medan)" method="GET">
    <table border="0" border="0" cellpadding="2px" cellspacing="2px" width="100%" bgcolor="">
        <tr>
            <td style="font-size:12px; text-align:left;" width="80%">
                <input id="search" name="search" type="text"/><input id="hidden" name="hidden" type="hidden"/>
            </td>
            <td style="font-size:12px; text-align:right;" width="20%">
                <input id="searchsubmit" name="Submit" value="Cari Produk" type="submit">

FYI: I am using Wordpress at my site.

Any ideas to change the url parameter like I want?
Thanks

Try something like this..... or You want something Different? Explain?

HTML

<form autocomplete="off" action="" onsubmit="return submitform()" method="POST">
    <table border="0" border="0" cellpadding="2px" cellspacing="2px" width="100%" bgcolor="">
        <tr>
            <td style="font-size:12px; text-align:left;" width="80%">
                <input id="search" name="search" type="text"/><input id="hidden" name="hidden" type="hidden"/>
            </td>
            <td style="font-size:12px; text-align:right;" width="20%">
                <input id="searchsubmit" name="Submit" value="Cari Produk" type="submit">
        </td>
        </tr>
        </table>
</form>

JAVASCRIPT

<script type="text/javascript">
function submitform()
{
    var hiddenFieldValue    =   document.getElementById('search').value;
        hiddenFieldValue    =   hiddenFieldValue.replace(/\s+/g, '-').toLowerCase();
        //alert(location.host+'/marketplace/tags/'+hiddenFieldValue);
        window.location         =   'http://'+location.host+'/marketplace/tags/'+hiddenFieldValue;
}
</script>