1. A method of developing and deploying a network application in a distributed computing system including at least a server and at least a client machine, wherein said client machine is adapted to connect to said server via a network, said method comprising: developing a server-side application comprising at least one markup document and at least one business logic component, wherein said markup document is written using any declarative Extensible Markup Language (XML) and said business logic component is written using any programming language; compiling said business logic component into a specific executable code using a compiler, wherein said compiler is adapted to receive a business logic component written in any programming language and to compile said business logic component into a specific executable code that can be executed by a specific execution engine in said client machine; converting said markup document into a specific markup language document using a markup language converter, wherein said markup language converter is adapted to receive a markup document written in any XML language and to convert said markup document into a specific markup language document that is compatible with a specific client runtime environment (CRE) of said client machine; and deploying said specific markup document and said specific executable code to said client machine via said network.