IOS UIWebView的字体大小控制

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    // finished loading, hide the activity indicator in the status bar
    [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    [self.guideWebView stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('body')[0].style.webkitTextSizeAdjust= '200%'"];
}