SEO - http code definition and IP address checkers

Search engine optimization:
The process of increasing the amount of visitors to a website by ranking high in the search results of a search engine.

Social bookmarking sites:
Basically, these are sites that allow users to post their favorite sites, using tags (or keywords) to categorize and organize them; then other users can take these bookmarks and add them to their own collection or share them with even more users.
del.icio.us, Digg, Reddit, Furl, StumbleUpon, Mixx
Fark, Propeller

Types of class checkers in SEO

Class a checker: IP addresses between 1.0.0.0 and 126.0.0.0. The first byte identifies the networks, the next 3 bytes the host. We have 127 networks and 16.777.216 hosts.
Class b checker
IP addresses between 128.0.0.0 and 191.255.255.255. The first 2 bytes identify the networks, the next 2 bytes the hosts. The first byte is limited to 128 - 191, so we have 16384 networks and 65536 hosts.
Class C: IP addresses between 192.0.0.0 and 223.255.255.255. The first 3 bytes identify the networks, the last byte the hosts. The first byte is limited to 192 - 223, so we have 2.097.152 networks and 256 hosts
Class D: it is used for multicast that is when just one host is broadcasting and all the others are receiving. Class ip ranges: 224.0.0.0 to 239.255.255.255
Class E: for future use (Experimental purpose only)
IP Range: 240.0.0.0 to 255.255.255.255

HTTP Status Codes that the Web Server can return - Definitions

1. 200 OK
2. 301 Moved Permanently
3. 302 Found
4. 304 Not Modified
5. 307 Temporary Redirect
6. 400 Bad Request
7. 401 Unauthorized
8. 403 Forbidden
9. 404 Not Found
10. 410 Gone
11. 500 Internal Server Error
12. 501 Not Implemented
13. 100 continue
14. 101 switching protocols
HTTP Status Codes 200 - The request has succeeded. The information returned with the response is dependent on the method used in the request.
HTTP Status Code - 301 Moved Permanently
The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs.
HTTP Status Code - 302 Found
The requested resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client SHOULD continue to use the Request-URI for future requests.
HTTP Status Code - 307 Temporary Redirect
The requested resource resides temporarily under a different URI. Since the redirection MAY be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires header field.
HTTP Status Code - 400 Bad Request
The request could not be understood by the server due to malformed syntax. The client SHOULD NOT repeat the request without modifications.
HTTP Status Code - 401 Unauthorized
The request requires user authentication. The response MUST include a WWW-Authenticate header field containing a challenge applicable to the requested resource.
HTTP Status Code - 403 Forbidden
The server understood the request, but is refusing to fulfill it. Authorization will not help and the request SHOULD NOT be repeated.
HTTP Status Code - 404 Not Found
The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent.
HTTP Status Code - 410 Gone
The requested resource is no longer available at the server and no forwarding address is known. This condition is expected to be considered permanent. Clients with link editing capabilities SHOULD delete references to the Request-URI after user approval.
If the server does not know, or has no facility to determine, whether or not the condition is permanent, the status code 404 Not Found SHOULD be used instead.
HTTP Status Code - 500 Internal Server Error
The server encountered an unexpected condition which prevented it from fulfilling the request.
HTTP Status Code - 501 Not Implemented
The server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource.
Optimizing joomla files
1. Change the default database prefix (jos_)
2. Remove version number / name of extensions
3. Use a SEF component
4. Change your .htaccess file
5. Use the correct CHMOD for each folder and file