function change_visibility() {
var blocks=new Array("one_month","three_months","three_days");
var p=new Array("first_period","second_period","third_period");
var pics=new Array("periodui_top","periodui_middle","periodui_bottom");

/*document.getElementById(blocks[1]).style.display = "block";*/

for(var i = 0; i<3; i++){
  if(document.surinkimo_forma.period[i].checked) {
    document.getElementById(blocks[i]).style.display = "block";
    /*document.getElementById('master_period').style.background = "url(pics/"+pics[i]+"-trans.png)";*/
    document.getElementById(p[i]).style.background = "#990000";
    }
  else {
    document.getElementById(blocks[i]).style.display = "none";
    document.getElementById(p[i]).style.background = "none";
    }
  }
}