rem: window.frames["messagepane"].location = "about:blank" 
add: window.frames["messagepane"].location = "about:blank";  HideMessageHeaderPane(); 
context: function ClearMessagePane(){    if (window.frames["messagepane"].location != "about:blank")        window.frames["messagepane"].location = "about:blank"}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/9c9c878a02898fc6f5a34a6570244a2895ce0fee/msgMail3PaneWindow.js/buggy/mailnews/base/resources/content/msgMail3PaneWindow.js