I find that if you use a lot of spaces, the browser will wrap it properly. Don't worry about using an exact number of spaces, just throw a lot in there, and the browser should properly wrap to the first non space character on the next line.

<textarea name="address" placeholder="1313 Mockingbird Ln         Saginaw, MI 45100"></textarea>

On most browser, editing the placeholder in javascript do allows multiline placeholder. As it has been said, it's not compliant with the specification.

This example replace all multiline textarea's placeholder.

var textAreas = document.getElementsByTagName('textarea');

Array.prototype.forEach.call(textAreas, function(elem) {
    elem.placeholder = elem.placeholder.replace(/\\n/g, '\n');
});

<textarea class="textAreaMultiligne" 
          placeholder="Hello,\nThis is multiline example\n\nHave Fun"
          rows="5" cols="35"></textarea>

Update:

Based on comments it seems some browsers accept this hack and others don't.
This is the result of tests I ran (with browsertshots.org and browserstack.com)

• Chrome: >= 35.0.1916.69
• Firefox: >= 35.0 (results varies on platform)
• IE: >= 10
• KHTML based browsers: 4.8
• Safari: No (tested = Safari 8.0.6 Mac OS X 10.8)
• Opera: No (tested <= 15.0.1147.72)

Base on statistics, this means that it works on about 88.7% of currently (Oct 2015) used browsers.

There is actual a hack which makes it possible to add multiline placeholders in Webkit browsers, Chrome used to work but in more recent versions they removed it:

First add the first line of your placeholder to the html5 as usual

<textarea id="text1" placeholder="Line 1" rows="10"></textarea>

then add the rest of the line by css:

#text1::-webkit-input-placeholder::after {
    display:block;
    content:"Line 2\A Line 3";
}

If you want to keep your lines at one place you can try the following. The downside of this is that other browsers than chrome, safari, webkit-etc. don't even show the first line:

<textarea id="text2" placeholder="." rows="10"></textarea>​

then add the rest of the line by css:

#text2::-webkit-input-placeholder{
    color:transparent;
}

#text2::-webkit-input-placeholder::before {
    color:#666;
    content:"Line 1\A Line 2\A Line 3\A";
}

Demo Fiddle

It would be very great, if s.o. could get a similar demo working on Firefox.

The html5 spec expressly rejects new lines in the place holder field. Versions of Webkit /will/ insert new lines when presented with line feeds in the placeholder, however this is incorrect behaviour and should not be relied upon.

I guess paragraphs aren't brief enough for w3 ;)

If your textarea have a static width you can use combination of non-breaking space and automatic textarea wrapping. Just replace spaces to nbsp for every line and make sure that two neighbour lines can't fit into one. In practice line length > cols/2.

This isn't the best way, but could be the only cross-browser solution.

<textarea class="textAreaMultiligne" 
          placeholder="Hello,&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; This&nbsp;is&nbsp;multiligne&nbsp;example Have&nbsp;Fun&nbsp;&nbsp;&nbsp;&nbsp;"
          rows="5" cols="35"></textarea>

If you're using AngularJS, you can simply use braces to place whatever you'd like in it: Here's a fiddle.

<textarea rows="6" cols="45" placeholder="{{'Address Line1\nAddress Line2\nCity State, Zip\nCountry'}}"></textarea>

You can try using CSS, it works for me. The attribute placeholder=" " is required here.

<textarea id="myID" placeholder=" "></textarea>
<style>
#myID::-webkit-input-placeholder::before {
    content: "1st line...\A2nd line...\A3rd line...";
}
</style>

Bootstrap + contenteditable + multiline placeholder

Demo: https://jsfiddle.net/39mptojs/4/

based on the @cyrbil and @daniel answer

Using Bootstrap, jQuery and https://github.com/gr2m/bootstrap-expandable-input to enable placeholder in contenteditable.

Using "placeholder replace" javascript and adding "white-space: pre" to css, multiline placeholder is shown.

Html:

<div class="form-group">
    <label for="exampleContenteditable">Example contenteditable</label>
    <div id="exampleContenteditable" contenteditable="true" placeholder="test\nmultiple line\nhere\n\nTested on Windows in Chrome 41, Firefox 36, IE 11, Safari 5.1.7 ...\nCredits StackOveflow: .placeholder.replace() trick, white-space:pre" class="form-control">
    </div>
</div>

Javascript:

$(document).ready(function() {
    $('div[contenteditable="true"]').each(function() {
        var s=$(this).attr('placeholder');
        if (s) {
            var s1=s.replace(/\\n/g, String.fromCharCode(10));
            $(this).attr('placeholder',s1);
        }
    });
});

Css:

.form-control[contenteditable="true"] {
    border:1px solid rgb(238, 238, 238);
    padding:3px 3px 3px 3px;
    white-space: pre !important;
    height:auto !important;
    min-height:38px;
}
.form-control[contenteditable="true"]:focus {
    border-color:#66afe9;
}

Watermark solution in the original post works great. Thanks for it. In case anyone needs it, here is an angular directive for it.

(function () {
  'use strict';

  angular.module('app')
    .directive('placeholder', function () {
      return {
        restrict: 'A',
        link:     function (scope, element, attributes) {
          if (element.prop('nodeName') === 'TEXTAREA') {
            var placeholderText = attributes.placeholder.trim();

            if (placeholderText.length) {
              // support for both '\n' symbol and an actual newline in the placeholder element
              var placeholderLines = Array.prototype.concat
                .apply([], placeholderText.split('\n').map(line => line.split('\\n')))
                .map(line => line.trim());

              if (placeholderLines.length > 1) {
                element.watermark(placeholderLines.join('<br>\n'));
              }
            }
          }
        }
      };
    });
}());

I do not think that is possible with html/css alone. Might be possible using JavaScript or some other kind of hack - extra spaces to push the text to the next line, etc.