I have been evaluating ESET Online Scan and Trend Micro HouseCall Online Scan since last couple of days. Both have a very good detection rate of known malwares. However, in this type of program module, ESET takes the lead as it offers other features like: Scan archives and Scan for potential unwanted apps. One more impressing feature of ESET is to scan password-protected archives. While scanning a 105 MB 7z archive, it made me wait for a few minutes but accurately detected Win32.Chir.B worm. ESET engine is always the favorite for detecting unknown malware and in my tests it detected variants of known malwares. Among the Cons of ESET online scan is that it takes a lot of time to update the definitions and it doesn't offer to scan a different path. You have to simply close the module. How is your experience with ESET web scan?