if (document.images) {
    work       = new Image();
    work.src   = "images/work.png" ;
    work_on     = new Image() ;
    work_on.src = "images/work_on.png" ;
	//
    news       = new Image();
    news.src   = "images/news.png" ;
    news_on     = new Image() ;
    news_on.src = "images/news_on.png" ;
    //
    contact       = new Image();
    contact.src   = "images/contact.png" ;
    contact_on     = new Image() ;
    contact_on.src = "images/contact_on.png" ;    
    //
    email       = new Image();
    email.src   = "images/email.png" ;
    email_on     = new Image() ;
    email_on.src = "images/email_on.png" ;
    //
    previous       = new Image();
    previous.src   = "images/previous.png" ;
    previous_on     = new Image() ;
    previous_on.src = "images/previous_on.png" ;    
    //
    next       = new Image();
    next.src   = "images/next.png" ;
    next_on     = new Image() ;
    next_on.src = "images/next_on.png" ;    
    //
    top       = new Image();
    top.src   = "images/top.png" ;
    top_on     = new Image() ;
    top_on.src = "images/top_on.png" ;    
}

function rollOver ( buttonname )
{
    if (document.images) {
      document[ buttonname ].src = eval( buttonname + "_on.src" );
    }
}

function rollOut( buttonname )
{
    if (document.images) {
      document[ buttonname ].src = eval( buttonname + ".src" );
    }
}