uuHEdt(uu Html Edit) is a Free Online Web-Based WYSIWYG HTML Editor that you can embed into your website to provide WYSIWYG HTML editing capabilities, and supports a wide variety of browsers such as IE, Opera, Firefox, Google Chrome and Safari.
It handles text formatting like bold, italics and underline, has table editing, a colour picker, the ability to insert images, set target window's size for insert a link, the ability to insert special characters, allows you to edit HTML code, etc.
The code is open source and is released under the The Code Project Open License (CPOL). It is used in Super Template content management system. 

Embed a HTML editor or a WYSIWYG web editor into your web site free of charge with the JavaScript code listed on this page. These scripts allow you to place an editor that allows your visitor to either create and edit HTML code using a WYSIWYG web interface or simply just write rich text with bold, underline, italics, font changes, etc, using a web interface. It is useful if you are creating an online application that requires the use of an online editor but don't want to spend a lot of time rolling your own. 

There are so many online html editors, and also they are so good. So, why another HTML Editor?
Yes, they are so good, but they are so BIG! I want a HTML Editor in my Super Template(a content management system), my system is small, even include page view(Template WYSIWYG design), process manager(load data/save data without coding), table and item manager, also with generating PDF files on-the-fly, the size of my system is not more than 500KB after zipped. But if use any ofTinyMCE(tinymce_3_2_7.zip is 660KB), CKEditor(FCKeditor_2.6.5.zip is 1.4MB), there are more big than the main part of my system. Of course, I tried others, but in the end, I developed the uuHEdt, small, but run on IE, Opera, Firefox, Google Chrome and Safari, also the panel can resized with window's size.
After packed, the size of uuHEdt's javascript is only 30KB.

1, add next in head.
<script type="text/javascript" src="sftab.js"></script>
<script type="text/javascript" src="uuhedt.js"></script>
* if you want to resize of floating window, then instead of sftab.js, you can use of ftab.js.
like next(should put ftab at the same directory of uuhedt):
<link rel="stylesheet" href="../ftab/ftab.css">
<link rel="stylesheet" href="../ftab/ftab_green.css">
<script type="text/javascript" src="../ftab/ftab.js"></script>
<script type="text/javascript" src="uuhedt.js"></script>

2, add div contents in body where you want to put uuhedt on.
<div id="editor" style="width:100%;height:220px;"></div>

3, after contents, add JavaScript to initialize Editor.
<script type="text/javascript">

function initEdt(){
var edt = UUHEdts.getEditor('editor');
edt.setContent('some html for edit.<br><i>sample text.</i>');
}
window.onload = initEdt;

</script>

Can add custom button to toolbar of uuHEdt.
see example page.