function formHandler(){
var URL = document.form.site.options[document.form.site.selectedIndex].value;
window.location.href = URL;
}

document.write('<form name="form">');
document.write('<select name="site" class=menubox size=1 onChange="javascript:formHandler()">');
document.write('<option value="index.htm">...Menu...');
document.write('<option value="javascript:history.go(-1);">...Previous Page...');
document.write('<option value="commercial.htm">Commercial');
document.write('<option value="rental.htm">Rental');
document.write('<option value="residentialproperties.htm">Residential');
document.write('<option value="services.htm">Services');
document.write('<option value="taxation.htm">Taxation');
document.write('<option value="zoning.htm">Zoning');
document.write('<option value="index.htm">Intro');
document.write('</select>');
document.write('</form>');