Redirection spam presents a web page with false content to a crawler for indexing, but automatically redirects the browser to a different web page. Redirection is usually immediate (on page load) but may also be triggered by a timer or a harmless user event such as a mouse move. JavaScript redirection is the most notorious of redirection techniques and is hard to detect as many of the prevalent crawlers are script-agnostic. In this paper, we study common JavaScript redirection spam techniques on the web. Our findings indicate that obfuscation techniques are very prevalent among JavaScript redirection spam pages. These obfuscation techniques limit the effectiveness of static analysis and static feature based systems. Based on our findings, we recommend a robust counter measure using a light weight JavaScript parser and engine. Categories and Subject Descriptors D.3.3 [Information Storage and Retrieval]: Information Search and Retrieval; H.3.m [Information Storage and Retrieval]: Miscel...