Several web browsers, including Google Chrome and Mozilla Firefox, use malware warnings to stop people from visiting infectious websites. However, users can choose to click through (i.e., ignore) these malware warnings. In Google Chrome, users click through a fifth of malware warnings on average. We investigate factors that may contribute to why people ignore such warnings. First, we examine field data to see how browsing history affects click-through rates. We find that users consistently heed warnings about websites that they have not visited before. However, users respond unpredictably to warnings about websites that they have previously visited. On some days, users ignore more than half of warnings about websites they've visited in the past. Next, we present results of an online, survey-based experiment that we ran to gain more insight into the effects of reputation on warning adherence. Participants said that they trusted high-reputation websites more than the warnings; however, their responses suggest that a notable minority of people could be swayed by providing more information. We provide recommendations for warning designers and pose open questions about the design of malware warnings.