achieved by associating a visitor segment with a predefined action. Customizing the user experience based on behavioral, contextual and technical data is proven to have a positive impact on conversion rate optimization efforts. Associated actions can range from changing the content of a webpage, presenting a modal display, presenting interstitials, triggering a personalized email, or even automating a phone call to the user. According to a 2014 study from research firm Econsultancy, less than 30% of e-commerce websites have invested in the field of web personalization. However, many companies now offer services for web personalization as well as web and email recommendation systems that are based on personalization or anonymously-collected user behaviors. There are many categories of web personalization including Behavioral Contextual Technical Historic data Collaboratively filtered There are several camps in defining and executing web personalization. A few broad methods for web personalization may include: Implicit Explicit Hybrid With implicit personalization, personalization is performed based on data learned from indirect observations of the user, such as items purchased on other sites or pages viewed. With explicit personalization, the web page (or information system) is changed by the user using the features provided by the system. Hybrid personalization combines the above two approaches to leverage both explicit user actions on the system and implicit data. Web personalization can be linked to the notion of Adaptive hypermedia (AH). The main difference is that the former would usually work on what is considered an "open corpus hypermedia", whilst the latter would traditionally work on "closed corpus hypermedia." However, recent research directions in the AH domain take both closed and open corpus into account. Thus, the two fields are closely inter-related. Personalization is also being considered for use in less overtly commercial applications to improve the user experience online. Internet activist Eli Pariser has documented that search engines like Google and Yahoo! News give different results to different people (even when logged out). He also points out social media site Facebook changes user's friend feeds based on what it thinks they want to see. Pariser warns that these algorithms can create a "filter bubble" that prevents people from encountering a diversity of viewpoints beyond their own, or which only presents facts which confirm their existing views. On an intranet or B2E Enterprise Web portals, personalization is often based on user attributes such as department, functional area, or role. The term "customization" in this