論文アブストラクト：In art and music, time periods like "classical" and "impressionist" are powerful means for academics and practitioners to compare and contrast artifacts that share aesthetics or philosophies. While web designs have undergone changes for 25 years, we lack theories to describe or explain these changes. In this paper, we take a first step towards identifying and understanding the design periods of websites. Drawing from humanistic HCI methods, we asked subject experts of web design to critically analyze a dataset of prominent websites whose lifetimes span over a decade. These informed judgments reveal a set of key markers that signal shifts in design periods. For instance, advances in display technologies and changes in company strategies help explain how design periods demarcated by particular layout templates and navigation models arise. We suggest that designers and marketers can draw inspiration from website designs curated into design periods. Future work should examine the utility of applying design periods to any computationally embedded artifact that is an interaction design.