Don't rely on the user's browser to be forgiving of bad HTML & CSS. CSS HTML Validator is designed to be nothing but the best tool there is for finding HTML, XHTML, and CSS problems in the easiest way possible.
It makes the critically important duty of checking your web documents as productive and thorough as possible.
The type of integrity control (checksum, HMAC, encryption, digital signature) should be directly related to the risk of the data transiting the trust boundary. However, validation should be performed as per the function of the server executing the code.
For example, the web / presentation tier should validate for web related issues, persistence layers should validate for persistence issues such as SQL / HQL injection, directory lookups should check for LDAP injection, and so on.
Server side validation is performed by a web server, after input has been sent to the server.
Client side validation is performed by a web browser, before input is sent to a web server.
Business rules are known during design, and they influence implementation.
Data from the client should never be trusted for the client has every possibility to tamper with the data.By commenting, you are accepting the DISQUS terms of service.To ensure that the application is robust against all forms of input data, whether obtained from the user, infrastructure, external entities or database systems. This weakness leads to almost all of the major vulnerabilities in applications, such as Interpreter Injection, locale/Unicode attacks, file system attacks and buffer overflows.For example, interest rates fall within permitted boundaries.Some documentation and references interchangeably use the various meanings, which is very confusing to all concerned.