JavaScript-only interfaces often have some links that activate some kind of click handler but don't actually go to another page. These are called JavaScript-only links, and there are a bunch of different ways to make them, listed here from crappiest to best:

• <a href="#" onclick="myFunc();return false">

  This method is really common, and not that great. If you are scrolled down the page, and forget to include the return false, the page will jump up to the top. Also, the user will see "#" in the status bar (not a real problem, but kind of messy). The link requires JavaScript to work. It's basically one big workaround for making some text clickable.

• <a href="javascript:myFunc()">

  This method gets a lot of slack, but I think it's slightly better than using href="#". True, it's a totally invalid href attribute, and it's pure luck that browsers actually support the javascript: protocol. But it works (if you have JavaScript enabled). And it has a slight benefit (or downside?) that users actually see the name of the function in the status bar, giving them a clue as to what is going on. You also don't need to worry about returning false from the click function.

• <a href="#myFunc" onclick="myFunc()">

  Very similar to using href="#", this method actually changes the URL to something slightly meaningful. This method can be useful if it changes the page in a repeatable way (displaying a specific tab or hidden area). This way you can add JavaScript that looks in the URL, sees the #myFunc, and recreates that change when the user refreshes the page. If you're tricky, you can even get the back and forward buttons to work. The downside: if the user has scrolled down, the page will scroll back to the top.

• <span onclick="myFunc()" style="text-decoration:underline; color:#00f; cursor:pointer">

  This is my favourite obtrusive method. If you're going to make a JavaScript-only link, why use a link at all? Anything can be clickable in JavaScript, and using CSS you can make a span look exactly like a link (even the mouse cursor). Downside: this method is still obtrusive, requiring JavaScript, but at least it's honest about it.

• <a href="alternate.html" onclick="myFunc();return false">

  This is a highly superior method to the others. If JavaScript is disabled, the link still works, and ideally goes somewhere that does the same stuff that the JavaScript function would do.

Disclaimer: I don't recommend using the onclick or style attributes on a regular basis. I also don't recommend making JavaScript-only interfaces ever (unless you have to, and you rarely have to). For more on how not to do all this bad stuff, check out my presentation on Unobtrusive Ajax.