The biggest advantage of the web survey method is that in many cases it is easier, faster and cheaper than any conventional methods. However, quality issues in web surveys are of interest because improving the quality of the survey process in terms of timeliness, response rate and accuracy is a basic requirement. The aim of this paper is to analyse several dimensions of quality of data collection through the web, adopting a mixed-mode contact and follow-up plan using both telephone and e-mail. In this way, we can compare differences between e-mail and telephone contact modes in response patterns on the occasion of both the first contact and the call-backs. Different quality indicators referring to data collection timeliness, the relationship between structural variables and quality of data collection process are computed. The data used on this empirical investigation concern university-to-work transition - an issue of great relevance in Italy considering its high levels of youth unemployment.