if (document.images) {

    img1on=new Image();  
    img1on.src="images/mainheader/toc1on.gif";     
    img1off=new Image(); 
    img1off.src="images/mainheader/toc1off.gif";  

    img2on=new Image();  
    img2on.src="images/mainheader/toc2on.gif";     
    img2off=new Image(); 
    img2off.src="images/mainheader/toc2off.gif"; 

    img3on=new Image();  
    img3on.src="images/mainheader/toc3on.gif";     
    img3off=new Image(); 
    img3off.src="images/mainheader/toc3off.gif"; 
    
    img4on=new Image();  
    img4on.src="images/mainheader/toc4on.gif";     
    img4off=new Image(); 
    img4off.src="images/mainheader/toc4off.gif";   

    img5on=new Image();  
    img5on.src="images/mainheader/toc5on.gif";     
    img5off=new Image(); 
    img5off.src="images/mainheader/toc5off.gif";  

    img6on=new Image();  
    img6on.src="images/mainheader/toc6on.gif";     
    img6off=new Image(); 
    img6off.src="images/mainheader/toc6off.gif"; 

    img7on=new Image();  
    img7on.src="images/mainheader/toc7on.gif";     
    img7off=new Image(); 
    img7off.src="images/mainheader/toc7off.gif"; 

    img8on=new Image();  
    img8on.src="images/mainheader/toc8on.gif";     
    img8off=new Image(); 
    img8off.src="images/mainheader/toc8off.gif"; 

}

// Function to 'activate' images.
function imgOn(imgName) {
if (document.images) {
    document[imgName].src=eval(imgName + "on.src");
}
}

// Function to 'deactivate' images.
function imgOff(imgName) {
if (document.images) {
    document[imgName].src=eval(imgName + "off.src");
    
}
}