Html – Is it safe to use to display images

I use javascript:void(0).

Three reasons. Encouraging the use of # amongst a team of developers inevitably leads to some using the return value of the function called like this:

function doSomething() {
    //Some code
    return false;
}

But then they forget to use return doSomething() in the onclick and just use doSomething().

A second reason for avoiding # is that the final return false; will not execute if the called function throws an error. Hence the developers have to also remember to handle any error appropriately in the called function.

A third reason is that there are cases where the onclick event property is assigned dynamically. I prefer to be able to call a function or assign it dynamically without having to code the function specifically for one method of attachment or another. Hence my onclick (or on anything) in HTML markup look like this:

onclick="someFunc.call(this)"

OR

onclick="someFunc.apply(this, arguments)"

Using javascript:void(0) avoids all of the above headaches, and I haven't found any examples of a downside.

So if you're a lone developer then you can clearly make your own choice, but if you work as a team you have to either state:

Use href="#", make sure onclick always contains return false; at the end, that any called function does not throw an error and if you attach a function dynamically to the onclick property make sure that as well as not throwing an error it returns false.

OR

Use href="javascript:void(0)"

The second is clearly much easier to communicate.

Using

$("a").attr("href", "http://www.google.com/")

will modify the href of all hyperlinks to point to Google. You probably want a somewhat more refined selector though. For instance, if you have a mix of link source (hyperlink) and link target (a.k.a. "anchor") anchor tags:

<a name="MyLinks"></a>
<a href="http://www.codeproject.com/">The CodeProject</a>

...Then you probably don't want to accidentally add href attributes to them. For safety then, we can specify that our selector will only match <a> tags with an existing href attribute:

$("a[href]") //...

Of course, you'll probably have something more interesting in mind. If you want to match an anchor with a specific existing href, you might use something like this:

$("a[href='http://www.google.com/']").attr('href', 'http://www.live.com/')

This will find links where the href exactly matches the string http://www.google.com/. A more involved task might be matching, then updating only part of the href:

$("a[href^='http://stackoverflow.com']")
   .each(function()
   { 
      this.href = this.href.replace(/^http:\/\/beta\.stackoverflow\.com/, 
         "http://stackoverflow.com");
   });

The first part selects only links where the href starts with http://stackoverflow.com. Then, a function is defined that uses a simple regular expression to replace this part of the URL with a new one. Note the flexibility this gives you - any sort of modification to the link could be done here.