source: http://www.securityfocus.com/bid/3122/info

An issue which affects users of multiple web browsers on Microsoft Windows platforms has been discovered.

Multiple malicious IMG tags may cause a denial of services to users who view webpages they are embedded into. Any medium which allows web users to embed a sufficient amount of HTML code that will be displayed to other users(forums, guestbooks, etc.) is a potential attack vehicle for a malicious user. Additionally, malicious webmasters may construct webpages which exploit this vulnerability.

The multiple malicious IMG tags will contain a unique 'mailto:' link, forcing the affected browser to open a corresponding number of e-mail compose windows. At the very least the browser will crash, but system resources may be exhausted enough to cause the entire machine to crash. 

Post 100+ IMG Tags, each with a unique 'mailto:' link.

<img src="mailto:johndoe1@example.com">
<img src="mailto:johndoe2@example.com">
etc.