You can insert a new line html entity 
 inside the placeholder attribute:

<textarea name="foo" placeholder="hello you&#10;Second line&#10;Third line"></textarea>

EDIT: Have tried with Chrome and works fine, but apparently this is not a cross-browser solution. Try implementing different solutions for other browsers. I think there is no global solution for this.

UPDATE (Jan 2016): The nice little hack might not work on all browsers anymore so I have a new solution with a tiny bit of javascript below.

A Nice Little Hack

It doesn't feel nice, but you can just put the new lines in the html. Like this:

<textarea rows="6" id="myAddress" type="text" placeholder="My Awesome House,
        1 Long St
        London
        Postcode
        UK"></textarea>

Notice each line is on a new line (not being wrapped) and each 'tab' indent is 4 spaces. Granted it is not a very nice method, but it seems to work:

http://jsfiddle.net/01taylop/HDfju/

• It is likely that the indent level of each line will vary depending on the width of your text area.
• It is important to have resize: none; in the css so that the size of the textarea is fixed (See jsfiddle).

Alternatively When you want a new line, hit return twice (So there is a empty line between your 'new lines'. This 'empty line' created needs to have enough tabs/spaces that would equate to the width of your textarea. It doesn't seem to matter if you have far too many, you just need enough. This is so dirty though and probably not browser compliant. I wish there was an easier way!

A Better Solution

Check out the JSFiddle.

• This solution positions a div behind the textarea.
• Some javascript is used to change the background colour of the textarea, hiding or revealing the placeholder appropriately.
• The inputs and placeholders must have the same font sizes, hence the two mixins.
• The box-sizing and display: block properties on the textarea are important or the div behind it will not be the same size.
• Setting resize: vertical and a min-height on the textarea are also important - notice how the placeholder text will wrap and expanding the textarea will keep the white background. However, commenting out the resize property will cause issues when expanding the textarea horizontally.
• Just make sure the min-height on the textarea is enough to cover your entire placeholder at its smallest width.**

HTML:

<form>
  <input type='text' placeholder='First Name' />
  <input type='text' placeholder='Last Name' />
  <div class='textarea-placeholder'>
    <textarea></textarea>
    <div>
      First Line
      <br /> Second Line
      <br /> Third Line
    </div>
  </div>
</form>

SCSS:

$input-padding: 4px;

@mixin input-font() {
  font-family: 'HelveticaNeue-Light', 'Helvetica Neue Light', 'Helvetica Neue', Helvetica, Arial, 'Lucida Grande', sans-serif;
  font-size: 12px;
  font-weight: 300;
  line-height: 16px;
}

@mixin placeholder-style() {
  color: #999;
  @include input-font();
}

* {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
}

form {
  width: 250px;
}

input,textarea {
  display: block;
  width: 100%;
  padding: $input-padding;
  border: 1px solid #ccc;
}

input {
  margin-bottom: 10px;
  background-color: #fff;

  @include input-font();
}

textarea {
  min-height: 80px;
  resize: vertical;
  background-color: transparent;
  &.data-edits {
    background-color: #fff;
  }
}

.textarea-placeholder {
  position: relative;
  > div {
    position: absolute;
    z-index: -1;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    padding: $input-padding;
    background-color: #fff;
    @include placeholder-style();
  }
}

::-webkit-input-placeholder {
  @include placeholder-style();
}
:-moz-placeholder {
  @include placeholder-style();
}
::-moz-placeholder {
  @include placeholder-style();
}
:-ms-input-placeholder {
  @include placeholder-style();
}

Javascript:

$("textarea").on('change keyup paste', function() {
  var length = $(this).val().length;
  if (length > 0) {
    $(this).addClass('data-edits');
  } else {
    $(this).removeClass('data-edits');
  }
});

Don't think you're allowed to do that: http://www.w3.org/TR/html5/forms.html#the-placeholder-attribute

The relevant content (emphasis mine):

The placeholder attribute represents a short hint (a word or short phrase) intended to aid the user with data entry when the control has no value. A hint could be a sample value or a brief description of the expected format. The attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

How about a CSS solution: http://cssdeck.com/labs/07fwgrso

::-webkit-input-placeholder::before {
  content: "FIRST\000ASECOND\000ATHIRD";
}

::-moz-placeholder::before {
  content: "FIRST\000ASECOND\000ATHIRD";
}

:-ms-input-placeholder::before {
  content: "FIRST\000ASECOND\000ATHIRD";
}

Salaamun Alekum




Works For Google Chrome

<textarea placeholder="Enter Choice#1 &#10;Enter Choice#2 &#10;Enter Choice#3"></textarea>

I Tested This On Windows 10.0 (Build 10240) And Google Chrome Version 47.0.2526.80 m

08:43:08 AST 6 Rabi Al-Awwal, 1437 Thursday, 17 December 2015

Thank You

Nope you cant do that in the placeholder attribute. You cant even html encode newlines like 
 in a placeholder.

A small demo:

http://jsfiddle.net/pdXRx/5/

You can't do it with pure HTML, but this jQuery plugin will let you: https://github.com/bradjasper/jQuery-Placeholder-Newlines

A slightly improved version of the Jason Gennaro's answer (see code comments):

var placeholder = 'This is a line \nthis should be a new line';
$('textarea').attr('value', placeholder);
$('textarea').focus(function(){
    if($(this).val() == placeholder){
        // reset the value only if it equals the initial one    
        $(this).attr('value', '');
    }
});
$('textarea').blur(function(){
    if($(this).val() == ''){
        $(this).attr('value', placeholder);
    }    
});
// remove the focus, if it is on by default
$('textarea').blur();

I liked the work of Jason Gennaro and Denis Golomazov, but I wanted something that would be more globally useful. I have modified the concept so that it can be added to any page without repercussion.

http://jsfiddle.net/pdXRx/297/

<h1>Demo: 5 different textarea placeholder behaviors from a single JS</h1>

<h2>Modified behaviors</h2>

<!-- To get simulated placeholder with New Lines behavior,
     add the placeholdernl attribute -->

<textarea placeholdernl>    (click me to demo)
Johnny S. Fiddle
248 Fake St.
Atlanta, GA 30134</textarea>

<textarea placeholder='Address' placeholdernl>    (click me to demo)
Johnny S. Fiddle
248 Fake St.
Atlanta, GA 30134</textarea>

<h2>Standard behaviors</h2>

<textarea placeholder='Address'>    (delete me to demo)
Johnny S. Fiddle
248 Fake St.
Atlanta, GA 30134</textarea>

<textarea>    (delete me to demo)
Johnny S. Fiddle
248 Fake St.
Atlanta, GA 30134</textarea>

<textarea placeholder='Address'></textarea>

The javascript is very simple

<script>
(function($){
var handleFocus = function(){
    var $this = $(this);
    if($this.val() === $this.attr('placeholdernl')){
        $this.attr('value', '');
        $this.css('color', '');
    }
};

var handleBlur = function(){
    var $this = $(this);
    if($this.val() == ''){
        $this.attr('value', $this.attr('placeholdernl'))
        $this.css('color', 'gray');
    }    
};

$('textarea[placeholdernl]').each(function(){
    var $this = $(this),
        value = $this.attr('value'),
        placeholder = $this.attr('placeholder');
    $this.attr('placeholdernl', value ? value : placeholder);
    $this.attr('value', '');
    $this.focus(handleFocus).blur(handleBlur).trigger('blur');
});
})(jQuery);
</script>

Try this:

<textarea
placeholder="Line1&#x0a;&#x09;&#x09;&#x09;Line2"
cols="10"
rows="5"
style="resize:none">
</textarea>

http://jsfiddle.net/vr79B/

Use 
 in place of /n this will change the line.

I modified @Richard Bronosky's fiddle like this.

It's better approach to use data-* attribute rather than a custom attribute. I replaced <textarea placeholdernl> to <textarea data-placeholder> and some other styles as well.

edited
Here is the Richard's original answer which contains full code snippet.

very simple

  var position = your break position;
    var breakLine = "
";//in html 
    var output = [value.slice(0, position), breakLine, value.slice(position)].join('');
    return output;

value represent the original string

Check out this solution with custom placeholder.

• You get multiline placeholder that works in all browsers (including Firefox)
• It is posible to customise placeholder as you want

Demo on fiddle.

$(document).on('input', '#textArea', function () {
	
        if ($('#textArea').val()) {
            $('#placeholderDiv').hide();
        } else {
            $('#placeholderDiv').show();
        }   
});

#textAreaWrap {
    position: relative;
    background-color: white;
}

#textArea {
    position: relative;
    z-index: 1;
    width: 350px;
    height: 100px;
    min-height: 100px;
    padding: 6px 12px;
    resize: vertical;
    background-color: transparent;
    /* When set background-color: transparent - Firefox  displays
    unpleasant textarea border. Set border style to fix it.*/
    border: 1px solid #a5a5a5;
}

#placeholderDiv {
    position: absolute;
    top: 0;
    padding: 6px 13px;
    color: #a5a5a5;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<div id="textAreaWrap">
    
<textarea id="textArea"></textarea>

<!-- Check here. If textarea has content -
     set for this div attribute style="display: none;" -->
<div id="placeholderDiv">Multiline textarea<br>
                         placeholder<br>
                         <br>
                         that works in Firefox</div>
    
</div>

HTML

<textarea data-placeholder="1111\n2222"></textarea>

JS

$('textarea[data-placeholder]').each(function(){
    var $this = $(this),
        placeholder = $this.data('placeholder'),
        placeholderSplit = placeholder.split('\\n');
    placeholder = placeholderSplit.join('\n');
    $this.focus(function(){
        var $this = $(this);
        if($this.val() === placeholder){
            $this.val('');
            // $this.removeClass('placeholder');
        }
    }).blur(function(){
        var $this = $(this);
        if($this.val() == '') {
            $this.val(placeholder);
            // $this.addClass('placeholder');
        }
    }).trigger('blur');
});

I don't like hiding the placeholder when you focus the textarea. So I made a constructor function Placeholder that looks exactly like the built-in placeholder and works also in other browsers than Google Chrome. It's very convenient because you can use the Placeholder function as often as you want and it doesn't even need jQuery.

EDIT:

It now also handles special cases, like inserting the placeholder, correctly.

var textarea = document.getElementById("textarea");
new Placeholder(textarea, "Line 1\nLine 2\nLine 3");

function Placeholder(el, placeholder) {
    if (el.value == "" || el.value == placeholder) {
        el.style.color = "gray";
        el.value = placeholder;
        el._plc = true;
        el.className += " unselectable";
    }
    function keyPress(e) {
        window.setTimeout(function() {
            var replaced = reverseStr(el.value).replace(reverseStr(placeholder), "");
            
            if (el.value == "") {
                el.value = placeholder;
                el.style.color = "gray";
                cursorToStart(el);
                el._plc = true;
                el.className += " unselectable";
            } else if (el._plc && el.value.endsWith(placeholder) && replaced !== "") {
                el.value = reverseStr(replaced);
                el.style.color = "black";
                el._plc = false;
                el.readOnly = false;
                el.className = el.className.replace("unselectable", "");
            } else if (el._plc && el.readOnly) {
                var ch = String.fromCharCode(e.charCode);
                if (e.keyCode == 13) ch = "\n";     // ENTER
                else if (e.charCode == 0) return;   // non-character keys
                
                el.value = ch;
                el.style.color = "black";
                el._plc = false;
                el.readOnly = false;
                el.className = el.className.replace("unselectable", "");
            }
        }, 10);
    }
    el.addEventListener("keypress", keyPress, false);
    el.addEventListener("paste", keyPress, false);
    el.addEventListener("cut", keyPress, false);
    el.addEventListener("mousedown", function() {
        if (el._plc) el.readOnly = true;
    }, false);
    el.addEventListener("mouseup", function() {
        el.readOnly = false;
        if (el._plc) cursorToStart(el);
    }, false);
  
    function cursorToStart(input) {
        if (input.createTextRange) {
            var part = input.createTextRange();
            part.move("character", 0);
            part.select();
        } else if (input.setSelectionRange){
            input.setSelectionRange(0, 0);
        } input.focus();
    }
    function reverseStr(str) {
        if (!str) return "";
        return str.split("").reverse().join("");
    }
}

textarea {
    border: 1px solid gray;
    padding: 3px 6px;
    font-family: Arial;
    font-size: 13px;
    transition: .2s;
}
textarea:hover, textarea:focus {
    border-color: #2277cc;
}
textarea:focus {
    box-shadow: inset 0 0 5px #85B7E9;
}
*.unselectable {
    -webkit-user-select: none;
    -webkit-touch-callout: none;
    -khtml-user-select: none;
    -moz-user-select: none;
    -ms-user-select: none;
    -o-user-select: none;
}

<textarea id="textarea"></textarea>