function nabidka(id){
if (document.getElementById(id).style.display == 'none')
document.getElementById(id).style.display='block';
else
document.getElementById(id).style.display='none';
}

<!--
cache1=new Image();
cache1.src="uploads/images/modely/cerna.jpg"; 
cache2=new Image(); 
cache2.src="uploads/images/modely/cervena.jpg"; 
cache3=new Image(); 
cache3.src="uploads/images/modely/seda.jpg";
cache4=new Image(); 
cache4.src="uploads/images/modely/modra.jpg"; 
cache5=new Image(); 
cache5.src="uploads/images/modely/modra.jpg"; 

function change_image(obr,nazev) 
{ 
obr.src= "uploads/images/modely/" + nazev + ".jpg"; 
return false;
}
// -->