<p>I'm thinking that the reason I can't do this is because it might be a huge security hole, but here goes...</p>

<p>I want to have a bookmark on my browser (FF3, preferably) that is only a snippet of javascript code.  It would merely construct a URL based on the current date and then do a window.location = on that URL.</p>

<p>I know that I could make a page and keep it on my local machine and just refer to it that way, but I was just wondering if you could bypass that step and actually have the "location" of the bookmark really just be javascript.  I could have sworn that this was possible years ago, but I can't find anything that tells me either way now.</p>

What you want is a
bookmarklet
they are easy to create and should work in most major browsers.
Edit: Stack overflow seems not to allow creating bookmarklets in the context of the site, basically you can create a new bookmark and type the following in the location field
```
javascript:window.location='http://www.google.com/search?q='+Date()
```
to get a bookmarklet that searches google for the current date.