字体大小

[webView stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '200%'"];

字体颜色

[webView stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('body')[0].style.webkitTextFillColor= 'gray'"];

页面背景色

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