This paper describes the design and evaluation of a web survey done for predicting performance for PhD students and their supervisors at university. The attractiveness of the example is that the web survey includes many kinds of questions, such as social network questions, socio-demographic questions, questions about publications, environment in the research group and attitudes towards work. Some of these questions were sensitive and complex to answer. We give a general overview about web survey design, advantages and inconveniencies over classics surveys (personal, telephone and mail) and afterwards we show our survey procedure. Some tips will also be suggested in order to improve response rates. Finally, the results for our web survey show that respondents are satisfied with the length, layout, difficulty, susceptibility and distribution of the questions. Moreover, we can differentiate between PhD students and supervisors in order to know which web survey characteristics we should take more in consideration when we are asking to junior or senior researchers.