if (document.images){
     Big_Over= new Image(172,70);
     Big_Over.src ="http://media.yalladownload.com/Images/V1/btn_download_over.jpg";  
     Small_Over= new Image(95,34);
     Small_Over.src ="http://media.yalladownload.com/Images/V1/btn_small_download_over.jpg";  
}

function BigOver(imgName) {
	if (document.images) { document.images[imgName].src= Big_Over.src;}
}
function BigOut(imgName) {
	if (document.images) { document.images[imgName].src ="http://media.yalladownload.com/Images/V1/btn_download.jpg"; }
}
function SmallOver(imgName) {
	if (document.images) { document.images[imgName].src= Small_Over.src;}
}
function SmallOut(imgName) {
	if (document.images) { document.images[imgName].src ="http://media.yalladownload.com/Images/V1/btn_small_download.jpg"; }
}