最近使用了UIWebView,发现当如下设置时
myWebView.backgroundColor = [UIColor clearColor];  
没有实现预期的透明效果
后来加上
myWebView.opaque = NO;  
myWebView.backgroundColor = [UIColor clearColor]; 
-(void)addWebView  
{  
    UIWebView *webView = [[UIWebView alloc]initWithFrame:CGRectMake(10, 10, 300, 200)];  
    webView.opaque = NO;  
    [self.view addSubview:webView];  
    webView.backgroundColor = [UIColor cleanColor];  
    NSString *ring = @"<h3>请客劵是什么?</h3><p><span style=\"font-size: 14px; background-color: rgb(0, 176, 240);\">请客劵是网站推送的拉动用户注册的一种优惠措施!</span><br/></p><h3><span style=\"font-size: 14px; background-color: rgb(0, 176, 240);\"><span style=\"font-size: 14px; background-color: rgb(255, 255, 255);\">请客劵有什么类型?</span><br/></span></h3><p><span style=\"font-size: 14px; background-color: rgb(0, 176, 240);\"><span style=\"font-size: 14px; background-color: rgb(255, 255, 255);\"><em>请客劵分为www.ifood517.com<span style=\"font-size: 14px; background-color: rgb(255, 255, 255); color: rgb(0, 112, 192);\">限非会员<span style=\"font-size: 14px; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0);\">和<span style=\"font-size: 14px; background-color: rgb(255, 255, 255); color: rgb(0, 112, 192);\">会员之分<span style=\"font-size: 14px; background-color: rgb(255, 255, 255); color: rgb(0, 0, 0);\">!</span></span></span></span></em><br/></span></span></p>";  
    [webView loadHTMLString:ring baseURL:[NSURL fileURLWithPath: [[NSBundle mainBundle] bundlePath]]];  
    webView.delegate = self;  
}  
- (void)webViewDidFinishLoad:(UIWebView *)webView {  
   // 禁用用户选择  
   [webView stringByEvaluatingJavaScriptFromString:@"document.documentElement.style.webkitUserSelect='none';"];  
   // 禁用长按弹出框  
   [webView stringByEvaluatingJavaScriptFromString:@"document.documentElement.style.webkitTouchCallout='none';"];  
}  
关于禁用长按webview后出现的功能项 最近get了一个新的方法, 用手势替换 感觉也是不错的
//添加手势 替换掉webView长按出现的功能选项  
UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:nil];  
longPress.delegate = self;  
longPress.minimumPressDuration = 0.4; //个人测试感觉0.4秒是最合适的时间  
[webView addGestureRecognizer:longPress];  
看看关于UIWebView的API
@property(nonatomic,readonly,retain) UIScrollView *scrollView NS_AVAILABLE_IOS(5_0);  
webview上其实是一个scrollview
[webView subviews] objectAtIndex:0];  //  这样就可以找到它了   
然后 想避免出现下拉阴影
- //禁掉 `scrollview`的回弹  
        [(UIScrollView *)[[webView_ subviews] objectAtIndex:0] setBounces:NO];
-  //隐藏
        for (UIView *subView in [webView_ subviews]) {  
               if ([subView isKindOfClass:[UIScrollView class]]) {  
                   for (UIView *shadowView in [subView subviews]) {  
                       if ([shadowView isKindOfClass:[UIImageView class]]) {  
                           shadowView.hidden = YES;  
                       }  
                   }  
               }  
           }