uiwebview 清缓存。，mark

//清除cookies
NSHTTPCookie *cookie;
NSHTTPCookieStorage *storage = [NSHTTPCookieStorage sharedHTTPCookieStorage];
for (cookie in [storage cookies]) 
{
    [storage deleteCookie:cookie];
}

UIWebView清除缓存：

//清除UIWebView的缓存
[[NSURLCachesharedURLCache] removeAllCachedResponses];