This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
AJAX has less security .
AJAX has a problem of data cache and many more .
Both of those are incorrect. There is no magical protocol that the XMLHttpReuest uses. The XMLHttpRequest uses basic http calls. Ajax is not any less secure than a normal http call. Caching problems are because a developer does not understand GET and Caching Headers on the requests/responses.