User-agent: K-Meleon/1.5
Through the oncontextmenu event attribute, web page authors can define a script action for certain page elements (or the entire page) when the user is right-clicking these elements (or the page). This attribute can be set statically in the HTML code of the page or dynamically through the DOM (JavaScript).
When dom.event.contextmenu.enabled is set to false, SeaMonkey and Firefox don't prevent websites from handling the event oncontextmenu, but they always show the browser's context menu when the specified script action is finished. K-Meleon however, does not show its own context menu in this situation, when the oncontextmenu attribute was set dynamically by a script.
See this test case:
http://freenet-homepage.de/CoolMcKluus/software/kmeleon/tests/nomenu.html
(Tests 2 and 4 are behaving different in K-Meleon and SeaMonkey/Firefox)
Bug 951 - JavaScript Context Menu Manipulation