19. A data display method making use of a user terminal and a data display server connected to a network to display prescribed data in response to a request from said user terminal, said method comprising the steps, performed by said data display server, of: creating through said user terminal, a message to be posted; inputting through said user terminal, a keyword of item data about contents of said message; retrieving said item data from said keyword; juxtaposing and displaying, on a display of the user terminal, one or more pieces of item data resulting from said retrieval; selecting through said user terminal, item data to be attached to posting data from said displayed item data; posting through said user terminal posting data containing an item data ID of the item data selected in said item data selecting step, the posting data including (i) the posting message, a posting ID identifying the posting message, and the item data ID having been posted through the user terminal and (ii) responsive posting data including a responsive posting message, a posting ID identifying the responsive posting message, and an item data ID; displaying, on the display of said user terminal in response to a posting data browsing request from the user, said posting data and item data specified by the item data ID contained in said posting data; and when the responsive posting data which is a reply to said posting data posted in said data display server exists, extracting the item data ID one by one from said posting data and said responsive posting data in accordance with a relationship between the posting data and the responsive posting data to generate relational metadata with said extracted item data IDs contained therein; wherein said item data is one or more pieces of information selected from a group comprising the item data ID, an item data name, an alias item data name, a model number, a manufacturer name, a category, a descriptive text, an image URL, a price, and a release date, said method further comprising juxtaposing and displaying on a display of said user terminal, said item data and relational data associated with said item data by said relational metadata, in response to an item data browsing request from the user, wherein said relational metadata associates the item data specified by the extracted item data IDs.
19. A data display method making use of a user terminal and a data display server connected to a network to display prescribed data in response to a request from said user terminal, said method comprising the steps, performed by said data display server, of: creating through said user terminal, a message to be posted; inputting through said user terminal, a keyword of item data about contents of said message; retrieving said item data from said keyword; juxtaposing and displaying, on a display of the user terminal, one or more pieces of item data resulting from said retrieval; selecting through said user terminal, item data to be attached to posting data from said displayed item data; posting through said user terminal posting data containing an item data ID of the item data selected in said item data selecting step, the posting data including (i) the posting message, a posting ID identifying the posting message, and the item data ID having been posted through the user terminal and (ii) responsive posting data including a responsive posting message, a posting ID identifying the responsive posting message, and an item data ID; displaying, on the display of said user terminal in response to a posting data browsing request from the user, said posting data and item data specified by the item data ID contained in said posting data; and when the responsive posting data which is a reply to said posting data posted in said data display server exists, extracting the item data ID one by one from said posting data and said responsive posting data in accordance with a relationship between the posting data and the responsive posting data to generate relational metadata with said extracted item data IDs contained therein; wherein said item data is one or more pieces of information selected from a group comprising the item data ID, an item data name, an alias item data name, a model number, a manufacturer name, a category, a descriptive text, an image URL, a price, and a release date, said method further comprising juxtaposing and displaying on a display of said user terminal, said item data and relational data associated with said item data by said relational metadata, in response to an item data browsing request from the user, wherein said relational metadata associates the item data specified by the extracted item data IDs. 20. The data display method according to claim 19 , further comprising: displaying the item data selected in said permitting the user to select step on a part of a posting display of said user terminal.