404 is the search for the number one masked killer.

Intermediary transaction http://www.aliyun.com/zixun/aggregation/6858.html ">seo diagnose Taobao guest cloud host technology Hall

Many websites inexplicably from the search to reduce the authority, stationmaster does not know is what reason. found that they did not cheat ah, but also do not know how to optimize ah, then why was sealed it. It's starting from 404.
I've also written a lot of articles like 404 that have been blocked from being searched.
404 error handling and the impact on SEO there is also an article about 404 conversion to 301 can alleviate the blocked
What is 404

400 cannot resolve this request.

401.1 Unauthorized: Access denied due to invalid credentials.

401.2 Unauthorized: Access was rejected because the server configuration tended to use alternate authentication methods.

401.3 Unauthorized: Access because the ACL's settings for the requested resource are denied.

401.4 Unauthorized: The filter authority installed on the WEB server failed.

401.5 Unauthorized: ISAPI/CGI application authorization failed.

401.7 Unauthorized: Access is denied because of a URL authorization policy on the WEB server.

403 Prohibit access: Access denied.

403.1 Prohibit access: execution access denied.

403.2 Prohibit access: Read access denied.

403.3 Prohibit access: Write access denied.

403.4 No access: You need to view the resource using SSL.

403.5 No access: You need to view the resource using SSL 128.

403.6 Prohibit access: The IP address of the client is denied.

403.7 No access: SSL client certificate required.

403.8 Prohibit access: The DNS name of the client is denied.

403.9 No access: Too many clients are trying to connect to the WEB server.

403.10 Prohibit access: The WEB server is configured to deny execution of access.

403.11 No access: password changed.

403.12 Prohibit access: The server certificate mapper has denied client certificate access.

403.13 Prohibit access: The client certificate has been revoked on the WEB server.

403.14 No access: The directory list has been rejected on the WEB server.

403.15 No access: The WEB server has exceeded the Client Access License limit.

403.16 No access: The client certificate is malformed or not trusted by the WEB server.

403.17 No access: The client certificate has expired or has not yet taken effect.

403.18 No access: The requested URL cannot be executed in the current application pool.

403.19 No access: CGI cannot be performed for clients in this application pool.

403.20 No access: Passport Login failed.

404 the file or directory could not be found.

404.1 file or directory not found: Web site cannot be accessed on the requested port.

Note that the 404.1 error occurs only on computers with multiple IP addresses. If a client request is received on a specific IP address/port combination and the IP address is not configured to listen on that particular port, IIS returns a 404.1 HTTP error. For example, if a computer has two IP addresses and only one of the IP addresses is configured to listen on port 80, any requests received from port 80 by another IP address will cause IIS to return 404.1 errors. This error should only be set at this service level because it is returned to the client only when more than one IP address is used on the server.

404.2 file or directory cannot be found: The lockdown policy prohibits the request.

404.3 file or directory cannot be found: The MIME mapping policy prohibits the request.

405 The HTTP action used to access the page is not licensed.

406 The client browser does not accept the MIME type of the requested page.

The 407 WEB server requires initial proxy authentication.

410 The file has been deleted.

412 The prerequisites for client setup failed when evaluated on the WEB server.

414 The request URL is too large, so the URL is not accepted on the WEB server.

500 Server Internal error.

500.11 Server Error: The application on the WEB server is shutting down.

500.12 Server Error: The application on the WEB server is rebooting.

500.13 Server Error: The WEB server is too busy.

500.14 Server Error: Invalid application configuration on server.

500.15 Server error: Direct request GLOBAL is not allowed. ASA.

500.16 Server Error: UNC authorization credentials are incorrect.

500.17 Server Error: URL authorization store could not be found.

500.18 Server Error: The URL authorization store could not be opened.

500.19 Server Error: The data for this file is not configured correctly in the metabase.

500.20 Server error: URL authorization domain could not be found.

500 100 Internal Server error: ASP error.

501 The specified configuration for the header value was not executed.

The 502 Web server received an invalid response as a gateway or proxy server.

Today, I received a call from a friend, who said that their company's website www.9mv.com a regular website was blocked by Baidu,
Http://www.baidu.com/s?wd=site%3A9mv.com&cl=3
They thought it was not before the purchase of the domain name was sealed, I first thought, will not be 404,
Then a look at WWW.9MV.COM/VSVF 404 was set up, which is estimated to be mostly this reason. If that's the reason. Sogou is probably not immune.
http://www.sogou.com/web?query=site%3A9mv.com sure did.

At present because 404 search is blocked the website many, the domestic tens of thousands of, I also most therefore was blocked, www.gjj.cc www.3tom.com www.7733.com www.666c.com

How to solve 404, there are many high man proposed to convert 404 to 301来 execution. I tried it, and it worked very well.
Publish The method
In server IIS, first define the 404 error to/404.htm and then define the 404.htm with 301 to the first page, or the wrong pages.

After I used this method, the search has never been sealed, a little experience, can be an amulet, protect you search undead.

Search engine to 404 wantonly blocked behavior also shows that the current search engine on the 404 SEO can not easily distinguish, and with heavy, across.
Is the search engine is very irresponsible performance. Also shows the helplessness of the search company.