||E-commerce and m-commerce have dramatically boosted the demand for services which enable ubiquitous access. Ubiquity offers new opportunities and challenges in terms of time-aware, location-aware, device-aware and personalized services. The fundamental objective of ubiquitous web applications is to provide services not only to people at any time, any where, with any media but specifically to communicate the right thing at the right time in the right way. The user should be enabled to interact efficiently with the application despite restrictions in the physical environment, thus preserving semantic equivalence of services and to take advantage from knowledge about the situation of use, leading to semantic enhancement of services. The pre-requisite for this is that the application is aware of it's context. For developing ubiquitous web applications, one must understand what context is to determine its relevancy and how it can be exploited for adapting the provided services towards this context, called customisation. Not least to customisation, the development of ubiquitous web applications is far from easy and calls for appropriate modelling techniques. There exists, however, only a few methods dedicated to the modelling of traditional web applications neglecting to a great extent ubiquity in terms of customisation. This thesis proposes a modelling method for ubiquitous web applications. Customisation is regarded as a new modelling dimension, influencing all other dimensions of ubiquitous web application modelling. As a prerequisite for supporting customisation, a set of generic models is introduced comprising a context model and a rule model, together with several sub models. Generic means that the models provide, in the sense of an object-oriented framework, pre-defined classes and language constructs in order to model customisation. For separation of concerns, the application is divided into a stable part, comprising the default, i.e., context-independent structure and behaviour and a variable, context-dependent part, thus being subject to adaptations. A set of generic adaptation operations is provided which can be complemented by application specific ones. These adaptation operations can be integrated into the ubiquitous web application on the basis of adaptation hooks. A customisation toolkit in terms of a customisation rule editor and browser supports an integrated modelling process and facilitates reusability on the basis of a repository of customisation rules, macros and patterns. Finally, a process is introduced, covering the whole task of customisation modelling, with a special focus on reusability, herewith providing a holistic view on the development process of ubiquitous web applications.