Simple html and css tooltip with newline/carriage return

Issue

I stumbled on a simple wonderful tooltip(http://cbracco.me/a-simple-css-tooltip/) but I'm unable to add a new line/ carriage return when I use it. I have tried
&013; \n but no success so far. I have also tried using the html inbuilt tooltip but it looks ugly in firefox.

Tooltip on hover:

Sentence one here. Sentence

two here. Sentence three here.

What I'm trying to output on hover:

Sentence one here.
Sentence two here.
Sentence three here.

<style>
/* Some basic styles */
*,
*:before,
*:after {
-webkit-box-sizing: border-box;
-moz-box-sizing:    border-box;
box-sizing:         border-box;
}

a:hover {
text-decoration: none;
}

/* Add this attribute to the element that needs a tooltip */
[data-tooltip] {
position: relative;
z-index: 2;
cursor: pointer;
}

/* Hide the tooltip content by default */
[data-tooltip]:before,
[data-tooltip]:after {
visibility: hidden;
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=0)";
filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=0);
opacity: 0;
pointer-events: none;
}

/* Position tooltip above the element */
[data-tooltip]:before {
position: absolute;
bottom: 150%;
left: 50%;
margin-bottom: 5px;
margin-left: -80px;
padding: 7px;
width: 160px;
-webkit-border-radius: 3px;
-moz-border-radius:    3px;
border-radius:         3px;
background-color: #000;
background-color: hsla(0, 0%, 20%, 0.9);
color: #fff;
content: attr(data-tooltip);
text-align: center;
font-size: 14px;
line-height: 1.2;
}

/* Triangle hack to make tooltip look like a speech bubble */
[data-tooltip]:after {
position: absolute;
bottom: 150%;
left: 50%;
margin-left: -5px;
width: 0;
border-top: 5px solid #000;
border-top: 5px solid hsla(0, 0%, 20%, 0.9);
border-right: 5px solid transparent;
border-left: 5px solid transparent;
content: " ";
font-size: 0;
line-height: 0;
}

/* Show tooltip content on hover */
[data-tooltip]:hover:before,
[data-tooltip]:hover:after {
visibility: visible;
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=100)";
filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=100);
opacity: 1;
}

</style> 

<a href="#" data-tooltip ="Sentence one here.
Sentence two here. 
Sentence three here.">Click for more details</a>

Solution

You can

EDIT: This corrects my previous answer that said you can't.

Because your CSS uses content: attr() to get the text inside a specified attribute, you can use an HTML entity code such as 
 to insert a newline.

Inserting a newline via an HTML entity code:

Note: You must set display: block and white-space: pre|pre-line|pre-wrap for the newline to display.

[data-tooltip] {
    cursor: default;
    font: normal 1em sans-serif;
}

[data-tooltip]:hover:after {
    display: inline-block;
    content: attr(data-tooltip);
    white-space: pre-wrap;
    color: Tomato;
    background-color: OldLace;
    padding: 1em;
}

<span data-tooltip="Sentence one here. Sentence&#xa;two here. Sentence three here.">See my CSS tooltip with HTML-entity &amp;#xa; line break:</span>

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This was also answered here: CSS data attribute new line character & pseudo-element content value

Answered By - gfullam