the font set by QWebSetting look smaller

i use one QWebview editWebView to edit text ,the code set the QWebView font :

settings()->setFontFamily(QWebSettings::StandardFont,"simsun" );
settings()->setFontSize(QWebSettings::DefaultFontSize,12);

i use another one QWebView displayWebView to display text ,using css to set text font,

<body style="font-family:â€˜simsunâ€™;font-size:12pt;color:#000000 ;"> ddddd </body>

but i found the text in editWebView look smaller than the text in displayWebView .
why?