Argumentation is considered as an activity that promotes learning and critical thinking. Learners who collaboratively argue about a subject are expected to acquire both knowledge and argumentation skills. However research indicates that we need to support both argument construction and collaboration. A form of support is employing computerized collaboration scripts to engage students in argumentation and regulate their activities. Such scripts have been proved to help students develop specific skills like the construction of single arguments or the argumentation sequence. Being an external support collaboration scripts should withdraw after students have internalized the skills they are supposed to, in order to be able to practice the acquired skills in similar tasks. To investigate the effect of scripting and fading on fostering argumentation skills we have built iArguea prototype web-based argumentation environment. In iArgue students are engaged in a jigsaw-type collaboration activity guided by a script that may gradually fade. The results from a preliminary expert-based evaluation were used to improve system design and propose for consideration ideas that could be taken into account when designing argumentation systems.