function switch_section(sec,sub){
    i = 0;
    do
    {
        var current_section = null;
        if ( document.all){
            current_section = document.all['section_'+sec+'_'+i];}
        else if ( document.getElementById ){
            current_section = document.getElementById('section_'+sec+'_'+i);}
        if ( current_section != null ){ 
            current_section.style.overflow = ( i == sub ? 'visible' : 'hidden' );
            current_section.style.visibility = ( i == sub ? 'visible' : 'hidden' );
        }
        i++;
    } while ( current_section != null );
}