Hide Show content-list with only CSS, no javascript used

I wouldn't use checkboxes, i'd use the code you already have

DEMO http://jsfiddle.net/6W7XD/1/

CSS

body {
  display: block;
}
.span3:focus ~ .alert {
  display: none;
}
.span2:focus ~ .alert {
  display: block;
}
.alert{display:none;}

HTML

<span class="span3">Hide Me</span>
<span class="span2">Show Me</span>
<p class="alert" >Some alarming information here</p>

This way the text is only hidden on click of the hide element

This is going to blow your mind: Hidden radio buttons.

input#show, input#hide {
    display:none;
}

span#content {
    display:none;
}
input#show:checked ~ span#content {
  display:block;
}

input#hide:checked ~ span#content {
    display:none;
}

<label for="show">
    <span>[Show]</span>
</label>
<input type=radio id="show" name="group">
<label for="hide">
    <span>[Hide]</span> 
</label>    
<input type=radio id="hide" name="group">
<span id="content">Content</span>