在webView的delegate回調方法 - (void)webViewDidFinishLoad:(UIWebView *)webView;中寫上一下語句即可

//字體大小

[webView stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '330%'"];

//字體顏色

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

//頁面背景色

[webView stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('body')[0].style.background='#2E2E2E'"];