function validateUsername(element) {
    if (element.value == "") {
        alert('Please enter a username.');
        return false;
    }
    /* check that username is between 3 and 15 characters long */
    if (element.value.length < 3 || element.value.length > 15) {
        alert('Username must be between 3 and 15 characters.');
        return false;
    }

    /* check that username is only alphanumeric characters */
    if ( !/^[\w-]+$/i.test(element.value) ) {
        alert('Username can only contain alphanumeric characters.');
        return false;
    }
    return true;
}

function dcHideLinks() {
  if (nav) {
    document.sitelinks.visibility = "hidden";
  } else {
    sitelinks.style.visibility = "hidden";
  }
} 

function dcHideLinksNav() {
  if (nav) {
    document.sitelinksnav.visibility = "hidden";
  }
  else {
    sitelinksnav.style.visibility = "hidden";
  }
}

function dcHideSearchLinksNav() {
    if (nav || document.searchlinksnav) {
    document.loadingImg.style.width = "138px";
    document.loadingImg.style.height = "25px";
    document.searchlinksnavImg.style.height = document.sitelinksnav.style.height;
        document.searchlinksnav.style.visibility = "hide";
    } else {
    loadingImg.style.width = "138px";
    loadingImg.style.height = "25px";
    searchlinksnavImg.style.height = searchlinksnav.style.height;
        searchlinksnav.style.display = "none";
    }
}

function doSearchSN(action) {
    var elem_username = $('c_screenname');
    if (action == "clear") { 
        if (elem_username.value == "screenname") {
            elem_username.value = "";
            elem_username.focus();
        }
    }
    if (action == "reset") {
        if (elem_username.value == "") {
            elem_username.value = "screenname";
        }
    }
    if (action == "go") {
        if (validateUsername(elem_username) && (elem_username.value != "" && elem_username.value != "screenname")) {
            dcHideSearchLinksNav();
            document.search_sn_form.submit();
        }
    }
}