if (document.images) {
 img1 = new Image();
 img1.src = 'images/butn_about_us_on.gif';
 img2 = new Image();
 img2.src = 'images/butn_contact_on.gif';
 img3 = new Image();
 img3.src = 'images/butn_customers_on.gif';
 img4 = new Image();
 img4.src = 'images/butn_design_on.gif';
 img5 = new Image();
 img5.src = 'images/butn_forms_on.gif';
 img6 = new Image();
 img6.src = 'images/butn_government_on.gif';
 img7 = new Image();
 img7.src = 'images/butn_login_on.gif';
 img8 = new Image();
 img8.src = 'images/butn_products_on.gif';
}