Rumors or abusive postings in internet have become a social issue. Web postings may be evidence in form of a screenshot in libel suit. A screenshot is an image which is taken by a computer and can be easily modified by computer programs. Users can write their message and modify some parts of writing or delete it after user authentication on a web site. A web server saves only the latest postings generally. So a person can make ill use of the screenshot which is modified deliberately original contents to opposite meaning in a lawsuit. That makes an innocent person to be punished because it can have difficulties to verify despite analyzing the server data. A screenshot of web postings is likely to fail to prove its authenticity and it is not able to reflect matter of fact that the screenshot of web postings has been modified. If notarization is offered for web posting evidence, clear and convincing evidence can be submitted in a court. So, related techniques and policies should be established. In this paper, we propose some technical and legal conditions and design for notarization and archive system of web postings for litigation.