rem: document.documentElement.getButton("back").disabled = true; 
add: this._wiz.canRewind = false; 
context:   onImportSourcePageShow: function ()  {    document.documentElement.getButton("back").disabled = true;        // Figure out what source apps are are available to import from:    var group = document.getElementById("importSourceGroup");    for (var i = 0; i < group.childNodes.length; ++i) {      var suffix = group.childNodes[i].id;      if (suffix != "nothing") {        var contractID = kProfileMigratorContractIDPrefix + suffix;        var migrator = Components.classes[contractID].createInstance(kIMig);        if (!migrator.sourceExists) {          group.childNodes[i].hidden = true;          if (this._source == suffix) this._source = null;        }      }    }        var firstNonDisabled = null;    for (var i = 0; i < group.childNodes.length; ++i) {	  if (!group.childNodes[i].hidden) {        firstNonDisabled = group.childNodes[i];        break;      }    }    group.selectedItem = this._source == "" ? firstNonDisabled : document.getElementById(this._source);  },
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/ac637ee7d44d8f9daaa297668e5a9240b6b49c6e/migration.js/clean/mail/components/migration/content/migration.js