function showTabContent(selTab) {

    var clearTabs = 1;
    var tab;
    var tabContent;
    var tabTD;
    var amount = 3;
    
    while (clearTabs <= amount) {
        tab = document.getElementById('tab' + clearTabs);
        tabContent = document.getElementById('tabContent' + clearTabs);
        tabTD = document.getElementById('tabTD' + clearTabs);

        tab.className = 'bg_tab';
        tabContent.style.display = 'none';
        tabContent.style.visibility = 'hidden';
        tabTD.className = 'tab';

        clearTabs++;
    }

    tab = document.getElementById('tab' + selTab);
    tabContent = document.getElementById('tabContent' + selTab);
    tabTD = document.getElementById('tabTD' + selTab);

    tab.className = 'bg_tab_active';
    tabContent.style.display = 'block';
    tabContent.style.visibility = 'visible';
    tabTD.className = 'tab_active';
}