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SEO Glossary

An ever-growing glossary of SEO Jargon

SEO Glossary » c

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Call-to-action (marketing)

A call to action (CTA) is a graphic or text on a website, meant to urge visitors to click, and continue down a conversion funnel. Calls to action are often found near the end of advertising copy, after readers have been primed to take action.

Examples of calls to action include: 'Get a Quote', 'Click Here', and 'Start Your Free Trial', often in the form of a button.

Canonical Attribute

The canonical attribute is a directive used to normalize URLs; that is, to indicate to search engines which is the preferred version of a web page for display in search results, should it have more than one URL.

The canonical attribute can be used in two ways:

  1. In the <head> section of all non-canonical versions of HTML content, e.g.: <link rel="canonical" href="http://www.example.com/services/foo.html">
  2. In the HTTP header, for non-HTML content, by responding with the Link rel="canonical", e.g.: Link: <http://www.example.com/downloads/white-paper.pdf>; rel="canonical"

Note that the canonical attribute is interpretted by search engines as a suggestion only, and other signals are considered in determining which page will appear in search.

See also: URL Normalization Top
See URL Normalization Top
Cascading style sheets

Cascading Style Sheets (CSS) is a computer language used for describing the visual presentation of web pages and other documents that use markup languages such as HTML.

CSS is designed to organize the construction of websites by separating web code that describes the look and presentation into external files, called style sheets. Style sheets contains all the instructions responsible for page layouts, fonts, and colours.

The separation of presentational data (using CSS) and content (embedded in HTML) makes web pages more accessible to more people, on more devices, and makes site development and maintenance less time-consuming than other, non-web standard technologies.

See also: HTML Top
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A citation is the mention of a business name, address, or phone number on the web. Citations are used as signals by search engines to help rank local businesses on their results pages. Citations are usually associated with online business directories and review sites, such as YellowPages.com, Yelp.com, Hotfrog.ca; however, citations can also be found in blog posts, social media profiles, and other, unstructured sources.

See also: Structured Citation Top
Clean code
See Semantic Markup Top
Clean URL

A clean URL is a URL that contains no query strings, which are often created along with dynamic web pages.

Example of an unclean URL and its query string:


Or worse yet:


Example of a clean URL structure, rewritten to contain only the path to a web page:


Clean URLs are user-friendly, being shorter, more memorable, logically structured, and descriptive. Also known as SEO-friendly URLs, clean URLs are typically structured with hierarchy and keywords that help search engines understand and index web pages.

See also: Query string Top
Click fraud

Click fraud is the illegal act of clicking on pay-per-click (PPC) ads solely to increase revenues for a website, or to deplete paid advertising budgets of competitors. Click fraud is performed both manually, and by using automated software.

Google, and other search engine companies have sophisticated means of differentiating between clicks that are fraudulent and those that show genuine interest in ads; however, detection isn't foolproof. Most experts estimate that 10% to 15% of PPC ad clicks are fake.

Click-through rate

A click-through rate (CTR) is the ratio of clicks that a link (usually a paid ad) receives to impressions, usually expressed as a percentage.

Click-through rates vary widely across advertising channels. Pay-per-click ads in search are higher than display ads such as banner ads, because of the targeted nature of PPC. A first place Google Adwords listing can have a click-through rate of 6% or more, whereas average CTRs for banner ads have dropped considerably—to approximately 0.2% in 2011—since they first appeared in the 1990's with average CTRs of over 3%.

Many factors influence click-through rates, including:


The succession of links that are clicked on while browsing one or more websites. Clickstream data is logged and analyzed for insights into visitor behavior as part of Web analytics


Generally speaking, cloaking refers to the deceptive practice of presenting content to visitors different from that which is served to search engines.

The primary goal of a cloaked web page is to rank well with often over-optimized, keyword-repetitive content, without having to display it to visitors.

Cloaking is considered black hat SEO, and can result in stiff indexing penalties from search engines, including removal of your website from their search results.

A widely publicized case of cloaking involved BMW's german website in 2006, resulting in Google temporarily de-indexing bmw.de[1].


See also: Spamdexing Top
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Comment spam

Comment spam refers to comments left on blogs solely for the purpose of acquiring a backlink. Because of the prevalence of comment spam, most blogging software devalues outgoing comment links with the use of no-follow attributes.

Comment spam is done both manually, and with the use of software that injects automated comments on blogs across the Web.

See Web Content Top

In marketing, a conversion is defined as a desired action being taken, such as a lead or purchase. Examples of online conversions include:

  • Membership registrations
  • Newsletter subscriptions
  • Software downloads
  • Product sales
  • Ad clicks
  • Contact form leads

The ratio of visits to conversions, or conversion rate, is a key performance indicator looked at in Web analytics, and is the ultimate measure of a website's success.

Conversion funnel

The conversion funnel is the path that website's visitor takes in a marketing process before making a purchase, downloading a file, or completing some other desirable action, or conversion.

Analyzing a website's conversion funnel is critical to understanding which points, or micro-conversions, are performing poorly on the way to ultimate goals, or macro-conversions.

Conversion rate

The percentage of web page visitors that take desired action, i.e., convert during a particular time period. It is generally accepted that conversion rates are normally in the low single-digits for most websites.

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("Copy" redirects here)

Copywriting is the art of writing for advertising or marketing purposes. Copywriters develop copy for web content, brochures, billboards, sales letters, and other commercial applications, including radio and television.

The goal of web copy is to engage and persuade visitors to take action, such as to purchase or download a product, or any other desirable conversion goal.

Copywriting for the Web is gradually moving away from overly aggressive marketing copy, towards subtly persuasive, user-friendly content that helps people make informed decisions.

Cost per action

("Pay per action" redirects here)

Cost per action (also known as pay per action), is an online advertising model based on payments made by the advertiser for specified actions taken by visitors, such as purchases, downloads, form submissions, and other completed conversions goals.

Cost per click
See Pay per click Top
See Cost per action Top
For 'cost per click', see Pay per click Top
See Web Crawler Top
See Cascading Style Sheets Top
CSS image replacement
See Image replacement Top
See Call-to-action Top
See Click-through rate Top
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