I have to admit I'm a bit saddened by the face that I could not find a single WYSIWYG HTML writing software that works in the cloud. Maybe the requirements are too high for an online app...I don't know. However I did find some tiny footprint programs that can be downloaded from the web and installed on the Netbook. If you don't want to have the power of Dreamweaver installed on your Netbook (or the amount of space this application takes up - 500MB and counting), here are some software recommendations for you.
KompoZer
KompoZer is a complete web authoring system that combines web file management and easy-to-use WYSIWYG web page editing. KompoZer is designed to be extremely easy to use, making it ideal for non-technical computer users who want to create an attractive, professional-looking web site without needing to know HTML or web coding.
KompoZer has both a WYSIWYG mode AND a coding mode, just like the big guys. It has a Site Manager function with built in FTP, and is available for PC, Mac and Linux machines. The best part is that KompoZer has a tiny download size (7.6 MB for Windows, 11.0 MB for Mac and 10.3 MB for Linux) - perfect for the Netbook!
SeaMonkey
SeaMonkey calls itself a "suite" of software packages built on the Mozilla source code. It contains a browser, email client, newsgroup client, HTML editor, IRC chat and web development tools. All I'm concerned about it whether or not it can write code in both a WYSIWYG format and code view. Composer is the name of the application included in the SeaMonkey application. It can do both, but they are not very robust. While utilizing a "tab" approach, the application does its job and nothing more. Many of the color cues in the code and basic features aren't there. It lets you write code and then preview it. Not bad, but just not interesting. It's just the basics.
SeaMonkey is larger than KompoZer (13MB for Windows, 23MB for Mac and 14MB for Linux) but contains all the applications in one download. Installation was easy. Check it out! At least the price is right!

Bluefish
The last one I want to bring to your attention is Bluefish. Although it is not a WYSIWYG writer (they call it a What You See is What You Need (WYSIWYN) interface!!!!!), it is an amazingly powerful text editor. If you started by writing your own code by hand, then this application will bring you back to those days. It's not only for writing web page code, but can also handle other programming languages as well. As a web guy, I appreciate the table and frame wizards and lots of tool-bars created especially for me. I loved this tool, but it can be intimidating for people who don't want to know code. I thought I would include it here for powerusers who may be thinking about a Netbook.