var target = "";

function jump(){

var url = document.form1.select.options[document.form1.select.selectedIndex].value;

if(url != "" ){

if(target == 'top'){
top.location.href = url;
}
else if(target == 'blank'){
window.open(url, 'window_name');
}
else if(target != ""){
eval('parent.' + target + '.location.href = url');
}
else{
location.href = url;
}

}

}