Recent years, many new theories and technologies for Web Wisdom have made the Web much wiser. Among these technologies, Cognitive-based text understanding (CTU) is one of the newest directions of Web Wisdom and should be paid more attention to. The machine understanding of Web resources is the basis of Web Wisdom. Cognitive Informatics (CI) is an emerging discipline that studies the natural intelligence, internal information processing mechanisms of the brain and the processes involved in perception and cognition as well. CTU simulates the cognitive process of human brain understanding text, so it takes advantage of cognitive theories to make the machine understanding of Web resources effectively and promotes Web Wisdom to a great extent. In this special issue on cognitive-based text understanding and web wisdom, we are pleased to present six papers. measures the semantic relatedness of Flickr images by measuring the semantic relatedness of tags and removing the noise and redundancy using bipartite graph. The second paper, " Extracting Visually Presented Element Relationships from Web Documents, " by Radek Burget and Pavel Smrz, proposes a formal generic model of logical relationships in a document based on an interpretation of visual presentation patterns in the documents. The model describes the visually expressed relationships between individual parts of the contents independently of the document format and the particular way of presentation.