(CSS) Height-Stretch with top: 0 and bottom: 0 with Pseudo-Element? - css

Question

I'm working on a two-column layout with float: left; and float: right; on two containers. To visually seperate these to container, I'd like to draw a vertical line between them via a Pseudo-Element in the parent container.
My code:
.twocol {
position: relative;
}
.twocol.divided:before {
content: "";
position: absolute;
top: 0;
bottom: 0;
left: 50%;
border-left: 2px dashed #000;
}
.leftcol {
float: left;
width: 50%;
padding-right: 20px;
}
.rightcol {
float: right;
width: 50%;
padding-left: 20px;
}
Then the html:
<div class="twocol divided">
<div class="leftcol">...</div>
<div class="rightcol">...</div>
</div>
With top: 0; and bottom: 0; the pseudo-element is supposed to draw a line from top to bottom of the parent .twocol. But nothing happens.
Using the same rules of the pseudo-element on an additional html-element div.divider inside of .twocol works well and draws the line. Is this technique not possible with pseudo-elements or am I missing out on something?
Here a jsfiddle.net/tw1vp2dg with the not working pseudo- and the working html-element examples.

Answer 1

You have display: table from you .twocol:before selector.
Add display: block or another value different from table to styles of your pseudo-element or remove .twocol:before selector.
Example

Answer 2

your overwriting your rule with your clearfix trick., drop it and use overflow:hidden on main container instead.
http://jsfiddle.net/tw1vp2dg/1/
erase this :
.twocol:before,
.twocol:after {
content: "";
display: table;
}
and add this instead
.twocol {
overflow:hidden;
}
* {
box-sizing: border-box;
}
body {
padding: 5px;
}
.twocol {
position: relative;
margin-bottom: 45px;
overflow:hidden;
}
.twocol.divided:before {
content: "";
position: absolute;
top: 0;
bottom: 0;
left: 50%;
border-left: 2px dashed #000;
}
.leftcol {
float: left;
width: 50%;
padding-right: 20px;
}
.rightcol {
float: right;
width: 50%;
padding-left: 20px;
}
.divider {
position: absolute;
top: 0;
bottom: 0;
left: 50%;
border-left: 2px dashed #000;
}
h1 {
font-size: 1.2em;
text-align: center;
}
// Clearfixing .twocol
.twocol {
zoom: 1;
}
.twocol:after {
clear: both;
}
<h1>Example with Pseudo-Element</h1>
<div class="twocol divided">
<div class="leftcol">
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. <br>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
</div>
<div class="rightcol">
Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. <br>Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. <br>Nam liber tempor cum soluta nobis eleifend option congue nihil imperdiet doming id quod mazim placerat facer.
</div>
</div>
<h1>Example with HTML-Element</h1>
<div class="twocol">
<div class="divider"></div>
<div class="leftcol">
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. <br>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
</div>
<div class="rightcol">
Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. <br>Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. <br>Nam liber tempor cum soluta nobis eleifend option congue nihil imperdiet doming id quod mazim placerat facer.
</div>
</div>