Our development focusses around web standards, and open standards. We usually develop websites and web applications with programming languages as PHP, Java, (Objective) C. For website front-end development, we create standards-based websites, styled using CSS, animated using Javascript and Ajax.
In both back-end development as well as font-end development, we apply principles of good design. Such as separation of content and presentation. For programming we usually follow the well-known three tier architecture of model, view, controller. For most of our projects, we work with UML-models to describe the architecture of the software, as well as the use cases.
Incidentally, we even find ourselves extending open source software for our specific needs, such as User Defined Functions (in MySQL) to perform operations that would otherwise be impossible.