Favlets are small snippets of JavaScript embedded in a Bookmark URL that allows Bookmarks in browsers do various advanced things. Popular Favlets include variants that prompts the user for a phrase and searches the web for that phrase, or that finds older versions of the currently viewed page in the WayBack Machine.
Favlets depend on support for javascript:
URLs
in your browser's Bookmarks feature, and each Favlet may depend on
support for a specific part of the JavaScript specification to work
properly. MSIE
versions more recent then 5.0, and Mozilla 1.0 and later — this
includes browsers using the embedded version of Mozilla, such as
Netscape 7.0 — are known to support most Favlets.
MSIE:mac
supports basic Favlets, but it's general support for JavaScript
may render certain advanced Favlets inoperable. Netscape 4.x is
a lost cause in this regard, and with it's poor support for standards
in general it is probably better to avoid it altogether.
Here There Be Dragons!