(new Image()).src = "img/bt1_2.jpg";
(new Image()).src = "img/bt2_2.jpg";
(new Image()).src = "img/bt3_2.jpg";
(new Image()).src = "img/bt4_2.jpg";
(new Image()).src = "img/bt5_2.jpg";
(new Image()).src = "img/bt6_2.jpg";


 
window.onload = function()
{
document.picture1.onmouseover = function(){ document.picture1.src="img/bt1_2.jpg"; }
document.picture1.onmouseout = function() { document.picture1.src="img/bt1_1.jpg"; }
document.picture2.onmouseover = function(){ document.picture2.src="img/bt2_2.jpg"; }
document.picture2.onmouseout = function() { document.picture2.src="img/bt2_1.jpg"; }
document.picture3.onmouseover = function(){ document.picture3.src="img/bt3_2.jpg"; }
document.picture3.onmouseout = function() { document.picture3.src="img/bt3_1.jpg"; }
document.picture4.onmouseover = function(){ document.picture4.src="img/bt4_2.jpg"; }
document.picture4.onmouseout = function() { document.picture4.src="img/bt4_1.jpg"; }
document.picture5.onmouseover = function(){ document.picture5.src="img/bt5_2.jpg"; }
document.picture5.onmouseout = function() { document.picture5.src="img/bt5_1.jpg"; }
document.picture6.onmouseover = function(){ document.picture6.src="img/bt6_2.jpg"; }
document.picture6.onmouseout = function() { document.picture6.src="img/bt6_1.jpg"; }
}