Web Science and Digital Libraries Research Group

  The CDC ACIP vaccine recommendations page includes a human-readable (left) and machine-readable (right) last updated date.  In early 2025, US federal websites were undergoing rapid changes with the new presidential administration. In February 2025, we analyzed the rate of page deletions across administrations, and further analyzed the content of changed CDC pages in summer 2025. One surprising thing that we found was that while CDC pages contained a “last updated” date, many of the dates were incorrect: pages contained silent, unannounced updates, generally related to relevant executive orders. How does trustworthiness change over time? Silent, unannounced changes that do not match the last modified date of a webpage reduce the trustworthiness of the page. We can study three different change markers: the HTTP last-modified property , meta tags that contain last updated information, and text on the page that is viewable to the user containing update information. These mar...

Figure 1: Example of an image pair from Reyes Ayala’s dataset of a live web page (left screenshot) and an archived web page (right screenshot) . For the Game Walkthroughs and Web Archiving project , we have created web archiving livestreams ( example livestream ) that use tools to measure the performance of a web archive crawler during the livestream. In a previous blog post , I compared six different approaches for measuring web archiving and replay performance metrics so that I could identify tools that could be used during our future web archiving livestreams. In this post, I will summarize another related work (“ Towards a better QA process: Automatic detection of quality problems in archived websites using visual comparisons ”) by Brenda Reyes Ayala that determines the quality of an archived web page by comparing screenshots of the live web page and archived web page.   Reyes Ayala, B. (2025). Towards a better QA process: Automatic detection of quality problems in archived we...

  Figure 1: Two extreme time zones – Baker Island (UTC-12:00) and Line Islands (UTC+14:00), adapted from International Date Line, Wikipedia . The International Date Line divides the world into multiple time zones. Initially, the idea was to divide the globe into 24 longitudinal slices, each about 15° wide. Theoretically, this would give us 24 time zones, each with a one-hour difference, defined by an offset from a reference time, the Coordinated Universal Time (UTC) .  In actuality, there are more than 24 time zones. Some regions use half-hour or even quarter-hour offsets rather than full hours - for example, Nepal ( UTC+5:45 ). In reality, time zones extend beyond 15° longitude because of political reasons, governance, economic aspects, geographical boundaries, and other conveniences. As a result, there are currently a total of 38 time zones . Extreme Time Zones, Side by Side The International Date Line is not a perfect straight line; rather it is a zig-zag to keep some r...