ugly :(
document.myForm.myInput.value
document.someImage.src

pretty :)
document.forms['myForm'].elements['myInput'].value
document.images['someImage'].src

How to extend the convenience of being able to shift-click links and open them in a new window to forms:

<form onsubmit="this.target=event.shiftKey?'_blank':'_self'">

Try it with the search-form (bottom of menu column): holding shift while submitting will open the search results in a new window.

Optimizing Javascript for speed - detailing some clever and interestingly named techniques: Loop Unrolling, Reverse Loop Counting, Loop Flipping and something called Duff's Device. [via scottandrew.com]

Wow, creating something interesting in under 256 bytes (for the 256b.htm compo) isn't easy... Here's one of the things I had to scrap: a random inkblot generator, way too big at 384 bytes... ;)

This one uses the XBM img src technique to generate a 2-bit image at run-time (example 1, 2). Could try rendering it with divs instead, but that'll probably cause quite the browser-freeze.

Include the following at the top of your Javascript:

  cookies = [];
  for (c in C=document.cookie.split('; '))
  {cookies[(cs=C[c].split('='))[0]]=unescape(cs[1]);}

  alert(cookies['myCookie']);

Please don't spawn popup-windows like this:
<a href="javascript:window.open('foo.html');">

or this:
<a href="#" onclick="window.open('foo.html');">

rather, use:
<a href="foo.html" onclick="window.open(this.href);return false;">

benefits:
- statusbar still indicates where you're going
- non-js users (and search-engines) still end up at the correct page
- current page doesn't jump to top (faux-anchor '#' evil)
- shift- and right-click options still open the correct page

Update:
Apparently using return false; in the href can mess up some browser's popup-blocking, so watch out if you care about that (haven't noticed it myself, but then again, I almost never use popups). [via]

Shortest syntax for preloading images in Javascript (in answer to a question by Wouterd yesterday):

for(i in ['larry.gif','moe.gif',
'curly.gif'])(new Image()).src=M[i];