HOW To Block pages via Robots.txt? GET Information About Robots.txt Rules and How to create robots.txt? How to optimize pages in robots.txt, disallow methods for search engines (seo) - applies to GOOGLE
These rules are latest ones by which one can optimize robots.txt for search engines by blocking unwanted urls, folders and unnecessary files.
The simplest robots.txt file uses two rules:
User-agent: the robot the following rule applies to
Disallow: the URL you want to block
These two lines are considered a single entry in the file. You can include as many entries as you want. You can include multiple Disallow lines and multiple user-agents in one entry.
Each section in the robots.txt file is separate and does not build upon previous sections. For example:
User-agent: *
Disallow: /folder1/
User-Agent: Googlebot
Disallow: /folder2/
In this example only the URLs matching /folder2/ would be disallowed for Googlebot.
Blocking user-agents - part1
The Disallow line lists the pages you want to block. You can list a specific URL or a pattern. The entry should begin with a forward slash (/).
To block the entire site, use a forward slash.
Disallow: /
To block a directory and everything in it, follow the directory name with a forward slash.
Disallow: /junk-directory/
To block a page, list the page.
Disallow: /private_file.html
To remove a specific image from Google Images, add the following:
User-agent: Googlebot-Image
Disallow: /images/dogs.jpg
To remove all images on your site from Google Images:
User-agent: Googlebot-Image
Disallow: /
To block files of a specific file type (for example, .gif), use the following:
User-agent: Googlebot
Disallow: /*.gif$
To prevent pages on your site from being crawled, while still displaying AdSense ads on those pages, disallow all bots other than Mediapartners-Google. This keeps the pages from appearing in search results, but allows the Mediapartners-Google robot to analyze the pages to determine the ads to show. The Mediapartners-Google robot doesn't share pages with the other Google user-agents. For example:
User-agent: *
Disallow: /
User-agent: Mediapartners-Google
Allow: /
Note that directives are case-sensitive. For instance, Disallow: /junk_file.asp would block http://www.example.com/junk_file.asp, but would allow http://www.example.com/Junk_file.asp. Googlebot will ignore white-space (in particular empty lines)and unknown directives in the robots.txt.
Pattern matching - part 2 ( advanced robots.txt )
Googlebot (but not all search engines) respects some pattern matching.
To match a sequence of characters, use an asterisk (*).
For instance, to block access to all subdirectories that begin with private:
User-agent: Googlebot
Disallow: /private*/
To block access to all URLs that include a question mark (?) (more specifically, any URL that begins with your domain name, followed by any string, followed by a question mark, followed by any string):
User-agent: Googlebot
Disallow: /*?
To specify matching the end of a URL, use $.
For instance, to block any URLs that end with .xls:
User-agent: Googlebot
Disallow: /*.xls$
You can use this pattern matching in combination with the Allow directive. For instance, if a ? indicates a session ID, you may want to exclude all URLs that contain them to ensure Googlebot doesn't crawl duplicate pages. But URLs that end with a ? may be the version of the page that you do want included. For this situation, you can set your robots.txt file as follows:
User-agent: *
Allow: /*?$
Disallow: /*?
The Disallow: / *? directive will block any URL that includes a ? (more specifically, it will block any URL that begins with your domain name, followed by any string, followed by a question mark, followed by any string).
The Allow: /*?$ directive will allow any URL that ends in a ? (more specifically, it will allow any URL that begins with your domain name, followed by a string, followed by a ?, with no characters after the ?).
source: www.google.com/support/webmasters/bin/answer.py?hl=en&answer=156449
