# A Sign of Things to Come: Predicting the Perception of Above-the-Fold Time in Web Browsing
## 1 Introduction  
As internet plays an increasingly important role in almost every workplace around the globe, web applications have gained a substantial role in streamlining different organizational, business, or personal processes. The success of web applications significantly depends on an providing a good user experience [1, 2]. Measuring the performance of web browsing is essential to understand how to improve the end-users' perceived quality or Quality of Experience (QoE) [3, 4]. According to [PERSON] et al. [5], QoE considers influence factors beyond service [5], i.e., context, user, content, and system factors. QoE covers the entire service experience and measures the degree of delight or annoyance of a user while using a service [5].  
In web browsing, when a web page is requested, the browser follows a process to fetch and render the web content on the user's screen. The end-user's QoE is partly dependant on how fast the visible page content is rendered in the browser [6]. Researchers have been actively developing metrics and models to estimate QoE of web browsing. Quality metrics (objective and subjective) and models are the critical components of web QoE analysis. Quality metrics measure the efficiency and performance of web applications. QoE models utilize objective quality metrics to estimate the perceived quality [7, 8].  
In 2012, Google introduced SpeedIndex (SI) [9] to estimate how fast a web page is visually completed, starting from the time that a URL is requested (URL request time) until the time that the visual content is completely painted on the current view-port of the screen (Above-the-fold (ATF) Time) [9]. In a user study conducted by the authors [10], however, it was established that if the website has an animation in the ATF area, the estimated ATF time may not accurately match completed ATF time reported by users. An inaccurate estimation of ATF will impact the perceived performance estimation metrics, like SI and QoE models, that rely on ATF estimation [10; 11].  
Motivated by our previous findings [10], in this paper, a visual metric that estimates ATF time in accordance with the users' perception is proposed. In order to differentiate it from ATF, which is an under-specified term, the metric is referred to as Plausibly Complete Time (PCT) as it is the time as which the metric predicts a page load to have plausibly competed rendering ATF content. PCT is designed to estimate the perceived ATF time for websites with different content characteristics, focusing on animated and non-animated content classes. The accuracy of the metric is evaluated based on data collected in the subjective study described in Reference [10] and a public dataset composed of page load data from 83 commercial websites [6]. The analysis shows that the proposed metric, PCT, is highly correlated with the perceived ATF time reported by the subjective study. Using PCT as a KPI in the IQX QoE model (exponential Interdependency of Quality of eXperience and QoS [7]) improves the robustness of QoE estimation in comparison to the objective ATF time. (Robustness in this paper refers to better approximating the performance under various network conditions and content characteristics (e.g., websites with or without animations).) Furthermore, it is observed that the estimation of SI using PCT improves the robustness of SI's speed estimation for webpages with and without animated contents.