1.获取网页高度 NSString *strHeight =[webView stringByEvaluatingJavaScriptFromString:@"document.body.offsetHeight"];

[webView stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('body')[0].style.background='#FFFFFF'"];

_webView.frame = CGRectMake(20, 10, G_SCREEN_WIDTH-40, [strHeight floatValue]);

_fheight = [strHeight floatValue]+10;