add: var hideButton = false;  try { if (gRedirectorType) { var prefs = Components.classes["@mozilla.org/preferences-service;1"].getService(Components.interfaces.nsIPrefBranch); var prefString = "mail.accountmanager." + gRedirectorType + ".hide_advanced_button"; hideButton = prefs.getBoolPref(prefString); } } catch (ex) { } if (hideButton) document.getElementById("server.advancedbutton").setAttribute("hidden", "true"); else document.getElementById("server.advancedbutton").removeAttribute("hidden"); 
context: function onPreInit(account, accountValues){    var type = parent.getAccountValue(account, accountValues, "server", "type", null, false);    gRedirectorType = parent.getAccountValue(account, accountValues, "server", "redirectorType", null, false);    hideShowControls(type);    if(!(account.incomingServer.isSecureServer))      document.getElementById("server.isSecure").setAttribute("hidden", "true");    else      document.getElementById("server.isSecure").removeAttribute("hidden");        if(!account.incomingServer.canEmptyTrashOnExit)    {      document.getElementById("server.emptyTrashOnExit").setAttribute("hidden", "true");      document.getElementById("imap.deleteModel.box").setAttribute("hidden", "true");    }}
meta: 8395	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/8395/e0cc9bc226e6b7ebcf41b6bcadfe560a77ed0c4b/am-server.js/clean/mailnews/base/prefs/resources/content/am-server.js