Vulnerabilities in Web browsers take many forms.
The vulnerabilities can be categorized into multiple classes including
Web page spoofing,
ActiveX control vulnerabilities,
Active scripting vulnerabilities,
MIME-type and content-type misinterpretation
Buffer overflows.

The consequences may include disclosure of cookies, local files or data, execution of local programs, download and execution of arbitrary code or complete takeover of the vulnerable system. To give some definition to their classes and add examples, the following general explanations with footnote references will followup on my consequitive blog postings.