What is a “call to action” on a site?

Call to action in web design — and in user experience (UX) in particular — is a term used for elements in a web page that solicit an action from the user. The most popular manifestation of call to action in web interfaces comes in the form of clickable buttons that when clicked, perform an action (e.g. “Buy this now!”) or lead to a web page with additional information (e.g. “Learn more…”) that asks the user to take action.
Call to Action Buttons: Examples and Best Practices by Smashing Magazine

It is literally a visual hint (or shout) that encourages a user to click or take some form of action.

Calls to action are used to:

• Direct a visitor’s eyes to a specific area of the web page.
• Encourage the visitor to click.
• Encourage the visitor to respond (comment, contact, submit, interact).
• Showcase information the visitor needs to know.
• Motivates action (promotes features, reasons to trust or purchase).

Examples of calls to action include images, links, and visual guides to:

• The contact form
• A survey
• Subscription
• Comment
• Join (membership)
• Sign up/Register
• Switch to a page with more information
• Watch a demo
• Purchase
• Alert or Warn
• Download
• Submit
• Save money (deals, coupons, etc.)
• Phone number, location, email, maps
• Words, not images, that instruct or pitch

Successful calls to action are measurable. Using web analytics, the site administrator can measure the clicks and responses to see if the call to action is working. If not, changes can be quickly made to improve it, testing as you go.

The following are articles to help you learn more about website and web design calls to action.

• Call to Action Buttons: Examples and Best Practices by Smashing Magazine
• Blogosphere Trends + Effective Calls to Action : @ProBlogger
• 15 Great Examples of Calls-to-Action for Lead Generation
• Google Analytics Event Tracking – Measure Calls to Action – Eugen Oprea
• 10 techniques for an effective ‘call to action’ | Boagworld
• 6 Tips for Creating a Good Call To Action – Blogging with Amy
• 7 Tips for Effective Calls to Action
• How to Create a Blog Sidebar That Converts Visitors Into Revenue
• 60 Effective Examples of Call to Action Buttons – DesignModo