Web surveys suffer from substantial nonresponse inducing nonresponse bias in estimates. Various groups cause nonresponse: initial nonrespondents and survey break-offs. A detailed understanding of the relative impact of initial nonresponse and survey break-offs is necessary to select proper strategies. Reducing survey break-off may cause additional measurement bias. Results indicate that the survey break-off bias and the initial nonresponse bias cancel each other and that responses of survey break-offs are less accurate. Therefore, survey break-off should not only be considered regarding the nonresponse bias prevention but also in terms of the measurement error.