下了一个例子，在家里跑的好好的，换了个机子就出问题了。Tomcat版本的一样的，出错如下：
[main] ERROR org.apache.myfaces.webapp.StartupServletContextListener  - Error initializing ServletContext
javax.faces.FacesException: java.io.IOException: Server returned HTTP response code: 403 for URL: http://java.sun.com/dtd/web-facesconfig_1_1.dtd

我的lib下有
myfaces-commons-1.1.2-SNAPSHOT.jar
myfaces-impl-1.1.2-SNAPSHOT.jar
myfaces-api-1.1.2-SNAPSHOT.jar
jsf-facelets-1.0.10.jar
jstl-1.1.2.jar

初步估计在家时能上网所以没有问题，换了个机子由于要用代理上网所以出现上面的403 错误。

web-facesconfig_1_1.dtd
明显是1.1版本
而你的myFaces则是1.2版本

应该如何更改？
我的faces-config开头如下
<!DOCTYPE faces-config PUBLIC
  "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.0//EN"
  "http://java.sun.com/dtd/web-facesconfig_1_0.dtd">

1.ERROR org.apache.myfaces.webapp.StartupServletContextListener - Error initializing ServletContext

初始化servletcontext错误

2.javax.faces.FacesException: java.io.IOException: Server returned HTTP response code: 403 for URL: http://java.sun.com/dtd/web-facesconfig_1_1.dtd

服务器返回响应错误代码403

3.不是JSF1.2的错误，因为，你的MYFACES并不是1.2而是1.1.2版本的

4.400 Invalid syntax. 语法问题
401 Access denied. 访问拒绝
402 Payment required. 必须完整
403 Request forbidden. 请求被禁止
404 Object not found. 对象没有找到
405 Method is not allowed. 方法不允许
406 No response acceptable to client found. 客户端没有响应
407 Proxy authentication required. 代理需要验证
408 Server timed out waiting for request. 等等请求时服务器断开连接
409 User should resubmit with more info. 有冲突用户应该进行检查
410 Resource is no longer available. 资源不可用
411 Server refused to accept request without a length. 服务器拒绝接受没有长度的请求
412 Precondition given in request failed. 放弃请求失败的条件
413 Request entity was too large. 请求太大
414 Request Uniform Resource Identifier (URI) too long. 请求的URI 太长
415 Unsupported media type. 不支持MEDIA类型
449 Retry after doing the appropriate action. 在作了适当动作后重试
500 Internal server error. 服务器内部错误
501 Server does not support the functionality required to fulfill the request. 服务器不支持请求的功能
502 Error response received from gateway. 从网关收到错误应答
503 Temporarily overloaded. 过载
504 Timed out waiting for gateway. 等待网关时请求断开
505 HTTP version not supported. 不支持HTTP的版本

HTTP status codes returned by servers on the Internet.
从Internet返回的HTTP status代码(HTTP 状态字)
HTTP_STATUS_CONTINUE (100)
The request can be continued.
请求不能被继续
HTTP_STATUS_SWITCH_PROTOCOLS (101)
The server has switched protocols in an upgrade header.
通过新的header服务器的协议被转换了
HTTP_STATUS_OK (200)
The request completed successfully.
请求成功的完成
HTTP_STATUS_CREATED (201)
The request has been fulfilled and resulted in the creation of a new resource.
通过新的资源请求已经被完成
HTTP_STATUS_ACCEPTED (202)
The request has been accepted for processing, but the processing has not been completed.
请求已经被接受处理，但是处理还没有完成
HTTP_STATUS_PARTIAL (203)
The returned meta information in the entity-header is not the definitive set available from the origin server.
从服务器返回的在entity-header中的meta信息是无效的
HTTP_STATUS_NO_CONTENT (204)
The server has fulfilled the request, but there is no new information to send back.
服务器实现了请求，但是没有返回信息
HTTP_STATUS_RESET_CONTENT (205)
The request has been completed, and the client program should reset the document view that caused the request to be sent to allow the user to easily initiate another input action.
请求已经被完成，并且web程序(客户端程序浏览器程序)已经重置了文档视图目录（content），这个目录很容易允许使用者用另一个动作发送请求
HTTP_STATUS_PARTIAL_CONTENT (206)
The server has fulfilled the partial GET request for the resource.
服务器已经为资源完成了部分GET请求
HTTP_STATUS_AMBIGUOUS (300)
The server couldn't decide what to return.
服务器不能判定返回什么
HTTP_STATUS_MOVED (301)
The requested resource has been assigned to a new permanent URI (Uniform Resource Identifier), and any future references to this resource should be done using one of the returned URIs.
被请求的资源已经被分配给新的URI,并且以后引用时都使用这个URIs资源。
HTTP_STATUS_REDIRECT (302)
The requested resource resides temporarily under a different URI (Uniform Resource Identifier).
请求的资源临时在不同的uri下
HTTP_STATUS_REDIRECT_METHOD (303)
The response to the request can be found under a different URI (Uniform Resource Identifier) and should be retrieved using a GET HTTP verb on that resource.
请求的资源不能在不同的uri下找到，并且从新使用GET HTTP在服务器上从新检索
HTTP_STATUS_NOT_MODIFIED (304)
The requested resource has not been modified.
请求的资源没有被改变
HTTP_STATUS_USE_PROXY (305)
The requested resource must be accessed through the proxy given by the location field.
请求的资源必须通过特定的代理获得
HTTP_STATUS_REDIRECT_KEEP_VERB (307)
The redirected request keeps the same HTTP verb. HTTP/1.1 behavior.
从定位请求，
HTTP_STATUS_BAD_REQUEST (400)
The request could not be processed by the server due to invalid syntax.
因为语法不能被服务器处理
HTTP_STATUS_DENIED (401)
The requested resource requires user authentication.
请求资源命令必须被验证（拒绝访问）
HTTP_STATUS_PAYMENT_REQ (402)
Not currently implemented in the HTTP protocol.
没有完全实现HTTP协议
HTTP_STATUS_FORBIDDEN (403)
The server understood the request, but is refusing to fulfill it.
服务器理解了请求，但是拒绝完成他
HTTP_STATUS_NOT_FOUND (404)
The server has not found anything matching the requested URI (Uniform Resource Identifier).
没有找到任何被指定的URI

HTTP_STATUS_BAD_METHOD (405)
The HTTP verb used is not allowed.
Http动作不被允许
HTTP_STATUS_NONE_ACCEPTABLE (406)
No responses acceptable to the client were found.
应答没有被客户接受
HTTP_STATUS_PROXY_AUTH_REQ (407)
Proxy authentication required.
代理必须被验证
HTTP_STATUS_REQUEST_TIMEOUT (408)
The server timed out waiting for the request.
服务器在等待请求时中止了
HTTP_STATUS_CONFLICT (409)
The request could not be completed due to a conflict with the current state of the resource. The user should resubmit with more information.
请求不能被完成，问题是资源冲突。用户应该进行调整
HTTP_STATUS_GONE (410)
The requested resource is no longer available at the server, and no forwarding address is known.
请求的资源在服务器上不再可用，而且没有转发地址
HTTP_STATUS_LENGTH_REQUIRED (411)
The server refuses to accept the request without a defined content length.
服务器拒绝接受没有定义目录大小的请求
HTTP_STATUS_PRECOND_FAILED (412)
The precondition given in one or more of the request header fields evaluated to false when it was tested on the server.
当在服务器上测试请求头文件放弃一个或者多个请求的条件
HTTP_STATUS_REQUEST_TOO_LARGE (413)
The server is refusing to process a request because the request entity is larger than the server is willing or able to process.
服务器拒绝处理请求，原因是请求的大小超过服务器能够处理的大小
HTTP_STATUS_URI_TOO_LONG (414)
The server is refusing to service the request because the request URI (Uniform Resource Identifier) is longer than the server is willing to interpret.
服务器拒绝服务，原因是请求的URI超过了服务器能够揭示的长度
HTTP_STATUS_UNSUPPORTED_MEDIA (415)
The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method.
服务器拒绝服务，原因是请求格式不被支持
HTTP_STATUS_RETRY_WITH (449)
The request should be retried after doing the appropriate action.
在作了适当的动作后请求被重试
HTTP_STATUS_SERVER_ERROR (500)
The server encountered an unexpected condition that prevented it from fulfilling the request.
服务器遇到请求失败意外
HTTP_STATUS_NOT_SUPPORTED (501)
The server does not support the functionality required to fulfill the request.
服务器不支持必须完成请求的功能
HTTP_STATUS_BAD_GATEWAY (502)
The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request.
服务器当作为网关或代理时，从上行服务器接受的响应请求失败
HTTP_STATUS_SERVICE_UNAVAIL (503)
The service is temporarily overloaded.
服务器负载
HTTP_STATUS_GATEWAY_TIMEOUT (504)
The request was timed out waiting for a gateway.
等待网关时请求断开，没有响应
HTTP_STATUS_VERSION_NOT_SUP (505)
The server does not support, or refuses to support, the HTTP protocol version that was used in the request message.
服务器不支持或者拒绝支持正在使用请求的HTTP协议的版本

你这里错误 描叙的也不是很详细

谢谢，2位的回答。
403的错误是因为我的Java虚拟机并未配置代理，所以在TOMCAT试图从网上下载http://java.sun.com/dtd/web-facesconfig_1_1.dtd时，被代理服务器返回的403错误。
我查看了lib下的所有jar,确实没有包含web-facesconfig_1_1.dtd这个文件，由于这个例子是我下的，所以不知道是不是缺少了什么 jar文件。

我的lib下有
myfaces-commons-1.1.2-SNAPSHOT.jar
myfaces-impl-1.1.2-SNAPSHOT.jar
myfaces-api-1.1.2-SNAPSHOT.jar
jsf-facelets-1.0.10.jar
jstl-1.1.2.jar

解决了~~~~~
把myfaces换成1.1.4就好了 -_-!!!