您应该允许从web.config访问Images文件夹。

例如我正在使用下一个设置：

< location path =Content / Images>

< system.web>

< identity impersonate = trueuserName =SomeUserpassword =UserPassword/>

< authorization>

< deny users =？/>

< / authorization>

< /system.web>

< / location>

You should allow from web.config the access to the Images folder.
For example I am using the next settings:
<location path="Content/Images">
<system.web>
<identity impersonate="true" userName="SomeUser" password="UserPassword"/>
<authorization>
<deny users="?"/>
</authorization>
</system.web>
</location>