ExecuteCode comprises of a system plugin and an editor button and allows you enter real code via your WYSIWYG without the code getting lost and you can even edit the code.

Add external code files inline

<link rel="stylesheet" type="text/css" href="http://demo.joomlashine.com/joomla-templates/jsn_air/pro/images/content-top/jquery.horizontal.scroll.css" />
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8/jquery.min.js"></script>
<script src="http://demo.joomlashine.com/joomla-templates/jsn_air/pro/images/content-top/js/jquery.horizontal.scroll.js" type="text/javascript"></script>
<script src="/media/joomlashine/jsn_air/custom.js" type="text/javascript"></script>

You can obviously also use

<style type="text/css">

</style>

<script type="text/javascript">

</script>

Incorrect Copy and Paste

When copying and pasting with Google Chrome there will be these A characters inserted where Tabs should be.

/* Test code */Â 
.dodgy-copy {
    display: inline-block;
    outline: medium none;
    padding: 4px;
    transition: all 300ms ease-out 0s;
}

Solution

Use firefox. I should probably look at updating my code.