default settings of phonegap webview is really not like a normal browser. I googled a lot to get it right. here is the tips in your main java file of phongap project , add these:
WebSettings settings = appView.getSettings(); 
settings.setPluginsEnabled(true);// Turn Flash plugin on, but you must install flash plugin yourself
settings.setBuiltInZoomControls(true);
settings.setSupportZoom(true);
settings.setDefaultZoom(ZoomDensity.MEDIUM); 
settings.setUseWideViewPort(true);
settings.setLoadWithOverviewMode(true);
after the line:
super.loadUrl(Config.getStartUrl());