This study investigates the 404 error and in what way feedback should be given to the user in an error message to generate a good user experience. To investigate this, data was gathered from 1) a literature review looking at previous studies in User Experience Design, as well as different models to evaluate ease of use and perceived usefulness, 2) a pre-study questionnaire with nine participants who were asked questions related to error messages and feedback in general, and 3) two user tests; the first including 16 participants and the second including 46 participants. During the user tests the participants interacted with a prototype of a website that included 404 error messages. In the first user test the participants' user experience was evaluated based on the TAM model, including perceived usefulness and perceived ease of use. The second user study focused more on text and illustrations and their effects on the user experience. Three versions of texts were tested, formal, apologetic and amusing. The illustrations either included a character or an object. The result showed that, in general, the users preferred formal texts, as well as illustrations that included a character. The result also suggested that there is not one type of feedback that fits all users, in order to generate a good user experience, it is important to know the audience.