context for an entire input formnot particular hyperlink an already entered usernamepasswordor selectionfor instancecan be implied by the values of hidden fields in subsequently generated pages in terms of codehidden fields are generated by server-side scripts as part of the reply page' html and are later returned by the client with all of the form' input data previewing the next usage againprint('urlrootprint('msgnumprint('userprint('siteprint('pswdlike query parametershidden form fields can also serve as sort of memoryretaining state information from page to page also like query parametersbecause this kind of memory is embedded in the page itselfhidden fields are useful for state retention among the pages of single session of interactionbut not for data that spans multiple sessions and like both query parameters and cookies (up next)hidden form fields may be visible to users--though hidden in rendered pages and urlstheir values still are displayed if the page' raw html source code is displayed as resulthidden form fields are not secureencryption of the embedded data may again be required in some contexts to avoid display on the client or forgery in form submissions http "cookiescookiesan oextension to the http protocol underlying the web modelare way for server-side applications to directly store information on the client computer because this information is not embedded in the html of web pagesit outlives the pages of single session as suchcookies are ideal for remembering things that must span sessions things like usernames and preferencesfor exampleare prime cookie candidates-they will be available the next time the client visits our site howeverbecause cookies may have space limitationsare seen by some as intrusiveand can be disabled by users on the clientthey are not always well suited to general data storage needs they are often best used for small pieces of noncritical cross-session state informationand websites that aim for broad usage should generally still be able to operate if cookies are unavailable operationallyhttp cookies are strings of information stored on the client machine and transferred between client and server in http message headers server-side scripts generate http headers to request that cookie be stored on the client as part of the script' reply stream laterthe client web browser generates http headers that send back all the cookies matching the server and page being contacted in effectcookie saving state information in cgi scripts