Despite the Wayback Maching, information disappears from the internet all the time. This includes information that you have cited in your scholarship. The 2012 article Something Rotten in the State of Legal Citation: The Life Span of a United States Supreme Court Citation Containing an Internet Link (1996-2010), 15 YALE J.L. & TECH. 273 (2012) demonstrated the issue for legal scholars and practitioners.
Perma.cc creates permanent links for scholars to use to preserve their internet citations. Contact law-refdesk@illinois.edu if you would like to use perma.cc. Zotero is a great option for creating a personal record of your research material.
Regardless of how you do it, it is always a good idea to preserve a copy of the content you use to support your research. Doing so, will help cite checkers approve your article and gives future scholars an opportunity to draw from the same sources you were able to use.
Legal scholarship is tracked by various means and for various purposes. It is important to make sure you are associated with all the work you produce. This will make it easier for employers to access your scholarly impact and for colleagues to find appropriate collaborators.
The University of Illinois maintains a database of scholarship by its faculty to facilitate collaboration and to celebrate their productivity called Illinois Experts.
HeinOnline is also endeavoring to correctly associate authors with their work, maintain a list of those works and the subsequent citations thereto.
Other disciplines use other metrics so if your work involves an interdisciplinary component it is worth investing in those systems.
