// preload main and sub menu background images
if (document.images) {
pic1= new Image(709,17);
pic1.src="images/menu_about.png"; 

pic2= new Image(709,17);
pic2.src="images/menu_company.png"; 

pic3= new Image(709,17);
pic3.src="images/menu_catalogue.png"; 

pic4= new Image(709,17);
pic4.src="images/menu_services.png"; 

pic5= new Image(709,17);
pic5.src="images/menu_contact.png"; 

pic6= new Image(120,15);
pic6.src="images/btn_misson.png"; 

pic7= new Image(120,15);
pic7.src="images/btn_overview.png"; 

pic8= new Image(120,15);
pic8.src="images/menu_operations.png"; 

pic9= new Image(120,15);
pic9.src="images/menu_linecard.png"; 

pic10= new Image(120,15);
pic10.src="images/menu_executives.png"; 

pic11= new Image(120,15);
pic11.src="images/menu_links.png"; 
}


// functions to change main menu background on button rollover
function btn_about() {
document.getElementById("menu_main").style.backgroundImage="url(images/menu_about.png)";;
}
function btn_company() {
document.getElementById("menu_main").style.backgroundImage="url(images/menu_company.png)";
}
function btn_catalogue() {
document.getElementById("menu_main").style.backgroundImage="url(images/menu_catalogue.png)";
}
function btn_services() {
document.getElementById("menu_main").style.backgroundImage="url(images/menu_services.png)";
}
function btn_contact() {
document.getElementById("menu_main").style.backgroundImage="url(images/menu_contact.png)";
}

// function to change main menu background to static image on rollout
function staticBackground() {
document.getElementById("menu_main").style.backgroundImage="url(images/menu_static.png)";
}