Glossary - I

image map
An image that has different clickable areas linked to different pages. Image maps can either be imbedded in the HTML code or called as an external file. Search engines usually have difficulty spidering image maps when they are included from external files.

impression
One display of an image or advertisement.

inbound link
When site A links to site B, site A has an outbound link and site B has an inbound link . Inbound links are counted to determine link popularity , an important factor in SEO . For more on link popularity, link building and the importance of inbound

index
Plural: indices / indexes.
Referring to the searchable database of documents stored by a search engine - often simply referred to as a search engine's database. When used as a verb, it describes the process of converting a collection into a searchable database. The term is sometimes also used to refer to directories like ODP .

index file
A file created by a search indexer program, designed to store information in a format that makes fast retrieval possible.

information extraction / information filtering
A field of study related to information retrieval that attempts to identify semantic structures in order to extract relevant data.

information retrieval
A field of study related to information extraction . Information retrieval is about developing systems to effectively index and search vast amounts of data.

intranet
Essentially a web site or group of (usually interlinked) web sites that is only accessible to people within a specific group or organization. Most large companies have intranets. Intranets offer a safe place for employees to publish information that improves workflow. Intranets typically house shared applications, internal telephone and e-mail directories, rules and regulations, help files etc. Many large intranets have a search facility that allows users to find specific information more easily.

inverted file
A file that represents a collection of documents or database . The inverted file lists all words that appear in all documents in the database, as well as a reference to the document where the word appears.

invisible text
Text on a web page that is exactly or almost the same color as the background. The use of invisible text to load a page with keywords was once a popular SEO technique, but search engines can now detect invisible text and penalize sites that use it. Although there are examples of sites that use invisible text and "get away with it" on Google , the general consensus is that it is not worth the risk. The same results can usually be achieved by working the keywords into the visible body text.

invisible web
A popular collective name for documents of types that search engines do not typically index . Because they are not in any search engine database , they can be very difficult to find and are in a sense invisible. Recently a couple of specialized search engines have begun an attempt to make the invisible web more accessible.

IP
Internet Protocol. Essentially a set of standards that are necessary to ensure that data sent between networks are readable on both sides. IP provides the standard for the way data is scrambled and sent over the Internet, while TCP (transmission control protocol) provides a standard for the way data is unscrambled. These two standards are essential to the working of the Internet.

IP address
Every Internet user and every server has a numeric address. Something like 123.45.67.890. IP addresses provide essential identification online. Domain names can be set up to have a unique IP address, something that is useful in SEO . For more on the role of IP addresses in SEO, please refer to the Search Engine Yearbook .

IP delivery
Similar to cloaking . A technique for automatically delivering different pages to different users based on the user's IP address . Although IP delivery has legitimate uses (like delivering different content to people from different geographical areas), it has been applied extensively in cloaking, causing IP based delivery to be banned by most search engines .

IP spoofing
A controversial technique for reporting a false IP address . In the context of search engines , IP spoofing is sometimes used to refer to the practice of cloaking .