Click Through Rate (CTR)
- ratio of the number of clicks on an advertisement against the number of page views, e.g. 6% CTR means for every 100 people who look at the advertisement, 6 will click on it.

Cloaking
- involves serving different content on a specific page to each search engine spider and human visitors. Usually frowned upon by search engines.

Doorway Page
- Any page created for the sole purpose of driving website traffic from the search engines, and is not a functional part of the website.

Google Adwords
- a pay-per-click (PPC) search engine marketing program by Google that allows you to advertise your products/services in Google's web site and its advertising network.

Google Dance
- The period during which Google updates its database causing fluctuation in search results.

Hits
- number of downloads from a web page, i.e. every item on a webpage counts as a hit. Thus, a single access on a webpage that contains 20 images will register as 21 hits - 20 for the images and 1 for the HTML page. Hits should be discounted when evaluating to advertise on a particular website, as opposed to other important traffic data like unique visitors and page views.

Java Script
- client-side scripting language that  runs on the user's computer rather than on web server, elements that are worthless from an SEO perspective.

Keyword Density
- the ratio of the number of occurrences of a particular keyword or phrase to the total number of words in a page. Normally we suggest about 10% for optimum effect.

Keyword Popularity
- the number of searches done by Internet users on a given keyword during a period of time.

Keyword Stuffing
- A technique where too many instances of the keyword are put into a web page without any context or use to make it keyword rich or increase keyword density. This practice is considered spamming by search engines and should be avoided at all times.

Link Building
- requesting backlinks from webmasters of other sites for the purpose of increasing your link popularity, usually through reciprocal link exchanges.

Meta Tags
- Meta information that is associated with a web page and placed in the HTML but not displayed on the webpage for human visitors. The 3 important meta tags are the meta title, meta description and meta keywords. Some internet marketing experts claim that meta keywords are no longer in use.

PageRank (PR)
- Google's search technology designed by Google's Larry Page to rank webpages on Google's search results. A webpage is ranked between a scale of 0 and 10. PageRanks are now only updated once in every 3~4 months.

Pop-Under
- a pop-up that appears underneath the currently active web browser window.

Pop-Up
- an annoying form of advertisement that appears in a new window, rather than the currently active browser window. The ads can be set to pop-up on entry, on exit or after a pre-defined time lapse.

Redirect
- where the site visitor is automatically taken to another webpage. Redirects are generally not good for SEO as they are known to "dilute" PageRanks.

Referrer
- the source the led a particular visitor to your webpage.

Reciprocal Linking
- the practice of trading links between webmasters for the purpose of exchanging traffic and increasing PageRank.

Search Engine
- a web site that offers its visitors the ability to search for content (e.g. information, products, etc.) on the Internet. Search engines periodically spider webpages and add the textual information into their index. Contrast this with a directory, that require human submission, editing and approval.

Search Engine Marketing (SEM)
- running marketing campaigns on search engines usually in the form of contextual ads, e.g. Google's Adwords program displays your Dell Inspiron laptop ad on the right-column in the search results for "Dell laptops", depending on your bid for that keyword phrase.

Search Engine Optimization (SEO)
- increasing your rankings on SERPs, and hence traffic, by optimizing the webpages for search engines, link building, etc.

Spider (aka bot, robot and crawler)
- programs used by a search engine to periodically explore your web site to retrieve information and store in its index. Spiders can also be used to automate tasks like checking links or validating codes, and sometimes for ill intentions like harvesting e-mail addresses for spam.

SERP
- acronym for Search Engine Results Page.

Traffic
- the amount of visitors to a website usually measured as unique visitors per day or per month.

Unique Visitors
- a count of individual visitors who have accessed your web site for a given period.

Web Directory
- a web site (usually about a certain topic) that contains links to other websites or resources. Unlike search engines, web directory listings are reviewed and added by human editors.