.: Search Engine Robots or Web Crawlers
By:Susmita
Category:Home / Internet Marketing / Search Engine Optimization
Most of the common users or visitors use different available search engines to search out the piece of information they required. But how this information is provided by search engines? Where from they have collected these information? Basically most of these search engines maintain their own database of information. These database includes the sites available in the webworld which ultimately maintain the detail web pages information for each available sites. Basically search engine do some background work by using robots to collect information and maintain the database. They make catalog of gathered information and then present it publicly or at-times for private use.
In this article we will discuss about those entities which loiter in the global internet environment or we will about web crawlers which move around in netspace. We will learn
· What it’s all about and what purpose they serve ?
· Pros and cons of using these entities.
· How we can keep our pages away from crawlers ?
· Differences between the common crawlers and robots.
In the following portion we will divide the whole research work under the following two sections :
I. Search Engine Spider : Robots.txt.
II. Search Engine Robots : Meta-tags Explained.
I. Search Engine Spider : Robots.txt
What is robots.txt file ?
A web robot is a program or search engine software that visits sites regularly and automatically and crawl through the web’s hypertext structure by fetching a document, and recursively retrieving all the documents which are referenced. Sometimes site owners do not want all their site pages to be crawled by the web robots. For this reason they can exclude few of their pages being crawled by the robots by using some standard agents. So most of the robots abide by the ‘Robots Exclusion Standard’, a set of constraints to restricts robots behavior.
‘Robot Exclusion Standard’ is a protocol used by the site administrator to control the movement of the robots. When search engine robots come to a site it will search for a file named robots.txt in the root domain of the site (http://www.anydomain.com/robots.txt). This is a plain text file which implements ‘Robots Exclusion Protocols’ by allowing or disallowing specific files within the directories of files. Site administrator can disallow access to cgi, temporary or private directories by specifying robot user agent names.
The format of the robot.txt file is very simple. It consists of two field : user-agent and one or more disallow field.
What is User-agent ?
This is the technical name for an programming concepts in the world wide networking environment and used to mention the specific search engine robot within the robots.txt file.
For example :
User-agent: googlebot
We can also use the wildcard character “*” to specify all robots :
User-agent: *
Means all the robots are allowed to come to visit.
What is Disallow ?
In the robot.txt file second field is known as the disallow: These lines guide the robots, to which file should be crawled or which should not be. For example to prevent downloading email.htm the syntax will be:
Disallow: email.htm
Prevent crawling through directories the syntax will be:
Disallow: /cgi-bin/
White Space and Comments :
Using # at the beginning of any line in the robots.txt file will be considered as comments only and using # at the beginning of the robots.txt like the following example entail us which url to be crawled.
# robots.txt for www.anydomain.com
Entry Details for robots.txt :
1) User-agent: *
Disallow:
The asterisk (*) in the User-agent field is denoting “all robots” are invited. As nothing is disallowed so all robots are free to crawl through.
2) User-agent: *
Disallow: /cgi-bin/
Disallow: /temp/
Disallow: /private/
All robots are allowed to crawl through the all files except the cgi-bin, temp and private file.
3) User-agent: dangerbot
Disallow: /
Dangerbot is not allowed to crawl through any of the directories. “/” stands for all directories.
4) User-agent: dangerbot
Disallow: /
User-agent: *
Disallow: /temp/
The blank line indicates starting of new User-agent records. Except dangerbot all the other bots are allowed to crawl through all the directories except “temp” directories.
5) User-agent: dangerbot
Disallow: /links/listing.html
User-agent: *
Disallow: /email.html/
Dangerbot is not allowed for the listing page of links directory otherwise all the robots are allowed for all directories except downloading email.html page.
6) User-agent: abcbot
Disallow: /*.gif$
To remove all files from a specific file type (e.g. .gif ) we will use the above robots.txt entry.
7) User-agent: abcbot
Disallow: /*?
To restrict web crawler from crawling dynamic pages we will use the above robots.txt entry.
Note : Disallow field may contain “*” to follow any series of characters and may end with “$” to indicate the end of the name.
Eg : Within the image files to exclude all gif files but allowing others from google crawling
User-agent: Googlebot-Image
Disallow: /*.gif$
Disadvantages of robots.txt :
Problem with Disallow field:
Disallow: /css/ /cgi-bin/ /images/
Different spider will read the above field in different way. Some will ignore the spaces and will read /css//cgi-bin//images/ and may only consider either /images/ or /css/ ignoring the others.
The correct syntax should be :
Disallow: /css/
Disallow: /cgi-bin/
Disallow: /images/
All Files listing:
Specifying each and every file name within a directory is most commonly used mistake
Disallow: /ab/cdef.html
Disallow: /ab/ghij.html
Disallow: /ab/klmn.html
Disallow: /op/qrst.html
Disallow: /op/uvwx.html
Above portion can be written as:
Disallow: /ab/
Disallow: /op/
A trailing slash means a lot that is a directory is offlimits.
Capitalization:
USER-AGENT: REDBOT
DISALLOW:
Though fields are not case sensitive but the datas like directories, filenames are case sensitive.
Conflicting syntax:
User-agent: *
Disallow: /
#
User-agent: Redbot
Disallow:
What will happen ? Redbot is allowed to crawl everything but will this permission override the disallow field or disallow will override the allow permission.
II. Search Engine Robots: Meta-tag Explained:
What is robot meta tag ?
Besides robots.txt search engine is also having another tools to crawl through web pages. This is the META tag which tells web spider to index a page and follow links on it, which may be more helpful in some cases, as it can be used on page-by-page basis. It is also helpful incase you don’t have the requisite permission to access the servers root directory to control robots.txt file.
We used to place this tag within the header portion of html.
Format of the Robots Meta tag :
In the HTML document it is placed in the HEAD section.
html
head
META NAME=”robots” CONTENT=”index,follow”
META NAME=”description” CONTENT=”Welcome to…….”
title……………title
head
body
Robots Meta Tag options :
There are four options that can be used in the CONTENT portion of the Meta Robots. These are index, noindex, follow, nofollow.
This tag allowing search engine robots to index a specific page and can follow all the link residing on it. If site admin doesn’t want any pages to be indexed or any link to be followed then they can replace “ index,follow” with “ noindex,nofollow”.
According to the requirements, site admin can use the robots in the following different options :
META NAME=”robots” CONTENT=”index,follow”> Index this page, follow links from this page.
META NAME=”robots” CONTENT =”noindex,follow”> Don’t index this page but follow link from this page.
META NAME=”robots” CONTENT =”index,nofollow”> Index this page but don’t follow links from this page
META NAME=”robots” CONTENT =”noindex,nofollow”> Don’t index this page, don’t follow links from this page.
Article keywords: SEO, SEM, Search Engine Optimization, Dynamic Page, robots, robots.txt
Article Source: http://www.articles32.com
Susmita love researching on web marketing and on SEO related issues. She prepared her blog for distributing knowledge and gathering knowledge as well as for sharing her views on different aspects of life.
.: New Search Engine Optimization Articles
1). How to Improve Search Engine Ranking
Powerful 4-step process to improve search engine ranking
2). How to Make Websites that Search Engines Love
How you can apply the fundamental basics to create a website that the search engines will love to spider.
3). Articles Are Seeds of Knowledge - A Biblical Look at Duplicate Content
Article Marketing compared to the successful distributon of the Christian Bible.
The Christian Bible is the Worlds most successful publication, with over 6 billion copies printed, similar to the total World Population.
4). Content Management Systems Equal Business Suicide!
One of the fastest way to minimise your chances of web business success is to use a Content Management System (CMS).
5). Importance of Search Engine Marketing Firms
Literally speaking, there is no business in todays world of World Wide Web, which doesnt have online business. To reach ever growing population of internet all across the world it is mandatory to have a good online presence for any business. Moreover, meeting customers online is the cheapest possible way.
6). Internet Search Engines, Important Details Everybody Should Know
Internet Search Engines see something totally different than what we see when we look at a webpage. It is all in the webpage code. Have you ever seen webpage code? Place one of your webpages into your browser.
7). Why Websites Get Banned From Search Engines
These are methods and techniques that end up getting websites banned from Google and other search engines.
.: Top Search Engine Optimization Articles
1). SEO Contests: Good or Bad?
As a webmaster you probably already know what a SEO Contest is or you surely came across some of them or even participated in. Some of the major SEO contests organized are the v7ndotcom elursrebmem (by v7n.com), Ambachdotcom, Carcasherdotcom, and more recently the Cpayscom2 Online Casino where the winner gets $10,000 for ranking number one on MSN. Now the big question is whether it is good or bad to organize SEO Contests.
2). High Paying Lateral Keywords
If you run AdSense on your site you know that some words pay more than others, much more in fact. More than likely you have also learned that terms like "structured settlements" and "mesothelioma" can produce incredibly high PPC revenue, if they show up on your site at all. Unfortunately hundreds of thousands of other webmasters are "on" to this practice judging by the number of sites created regularly to capitalize on the phenomenom.
3). Is Your Website Invisible? The Google Sandbox Solution
What is the Google Sandbox? How Do You Know if You’re Stuck in the Sandbox? Does the Sandbox Really Exist, or is it Just the Google Algorithm? Why Do You Get Sandboxed? Is There a Way to Trick the Sandbox Filter?
4). An SEO Glossary - Common SEO Terms Defined
Search Engine Optimization (SEO) has become an essential weapon in the arsenal of every online business. Unfortunately, for most business owners and marketing managers (and even many webmasters), it's also somewhat of an enigma. This is partly due to the fact that it's such a new and rapidly changing field, and partly due to the fact that SEO practitioners tend to speak in a language all of their own which, without translation, is virtually impenetrable to the layperson.
5). Creating Sitemaps For Google, MSN AND Yahoo! - The Easy Way
If you own or maintain a website or intend to own one, wouldn’t it be great if you get frequent visitors who find satisfaction in getting exactly the information they need from your page?
While that satisfaction largely depends on the contents of your website, how you get to be accessed by website users is the most critical factor of website development.
6). How to Make a Sitemap For Your Website In Five Steps.
A website's sitemap can be compared to the table of contents of a book. The sitemap is important because it guides visitors to the parts of the website in which they are interested. The sitemap allows surfers to reach their destination without wasting time.
Sitemaps are also important from the point of view of search engines. If the search engine finds a sitemap it is much more likely that your page will be fully visited (spidered) and indexed; allowing web surfers to find your pages in their searches.
7). 301 Redirect - The SEO way to rename or move files or folders
In this article I will discuss page redirection techniques, what works and what to avoid.
What is page redirection and why would you want to use it?
Let’s say you rename a page on your website, for whatever reason. Perhaps you decided to revamp your entire naming convention, perhaps you decided to restructure your site and need to move pages into different folders, or you just realized that you are missing valuable keywords.