function about_drop1(){
document.getElementById('about_drop').style.display="block";
}
function about_drop2(){
document.getElementById('about_drop').style.display="none";
}
function service_drop1(){
document.getElementById('service_drop').style.display="block";
}
function service_drop2(){
document.getElementById('service_drop').style.display="none";
}
function product_drop1(){
document.getElementById('product_drop').style.display="block";
}
function product_drop2(){
document.getElementById('product_drop').style.display="none";
}