Skipfish is an active web application security reconnaissance tool. It prepares an interactive sitemap for the targeted site by carrying out a recursive crawl and dictionary-based probes. The resulting map is then annotated with the output from a number of active (but hopefully non-disruptive) security checks. The final report generated by the tool is meant to serve as a foundation for professional web application security assessments.
Mercurial is a version control system. Developers use it to manage source code. It serves two important purposes:
1. It keeps track of every old version of every file
2. It can merge different versions of your code, so that teammates can work independently on the code and then merge their changes