function zav(idecko){
zavorka1=document.getElementById(idecko + "_l").style; 
zavorka1.visibility=(zavorka1.visibility == 'visible')?'hidden':'visible';
zavorka2=document.getElementById(idecko + "_r").style; 
zavorka2.visibility=(zavorka2.visibility == 'visible')?'hidden':'visible';
}
function zav_t(idecko){
zavorka1=document.getElementById(idecko + "_l").style; 
zavorka1.display=(zavorka1.display == 'inline')?'none':'inline';
zavorka2=document.getElementById(idecko + "_r").style; 
zavorka2.display=(zavorka2.display == 'inline')?'none':'inline';
}
function div_proj(idecko){
zavorka1=document.getElementById(idecko).style; 
zavorka1.display=(zavorka1.display == 'block')?'none':'block';
}