The content type is a declaration that is usually placed in the header of a web page, the so-called HTTP header. This declaration defines the character set and the type of data that the page contains. If the definition is missing, the web browser will try to guess the content type; this can lead to security flaws such as Code-Page-Sniffing. This information is also important for rendering the web page correctly in every browser and on every computer. If a server sends a document to a User Agent (for example to the browser), it is helpful to supply some information about the file format in the content type field of the HTTP header. This information declares the MIME type and sends the character encoding of the document, such as text/html, text/plain, etc. to the browser.