function toTab(pageName,elmnt,color) {
    var i, tabcontent, tablinks;
    tabcontent = document.getElementsByClassName("extra-content");
    for (i = 0; i < tabcontent.length; i++) {
      tabcontent[i].style.display = "none";
    }
    tablinks = document.getElementsByClassName("tab");
    for (i = 0; i < tablinks.length; i++) {
      tablinks[i].style.borderColor = "";
    }
    document.getElementById(pageName).style.display = "inherit";
    elmnt.style.borderColor = color;
}