From What I have checked problem can be reproduced from CKEditor 3.0 in Blink and Webkit browsers.
Additionally in Firefox the result is also not as expected. When checking it with Firebug it looks like:
<div style="background:red;">some red text</div>
<br>
<div style="background:blue;">some blue text</div>
After switching to source:
<div style="background:red;">some red text</div>
<p>
<div style="background:blue;">some blue text</div>
</p>
}}}}
Which after switching to wysiwyg looks like:
{{{
<div style="background:red;">some red text</div>
<p> </p>
<div style="background:blue;">some blue text</div>
<p> </p>
}}}
