Working with html on geocaching.com is simple.
Check the html box
Paste code you've created from editor. Try Notepad++ which gives great syntax highlighting for html (and other scripting languages.) Once you see the html syntax in color you are on your way to leaving Dreamweaver in the dust, imho.
Also, if geocaching.com had a proper wysiwyg editor, like ckeditor, we wouldn't be formatting and inserting using other programs, like Word or Dreamweaver. And with a proper built-in-to-the-form editor we could even paste-in a word .doc and it would strip out all the spaghetti at the click of a button.
Then, save it and check it, on a big monitor and on a tiny gpsr display.
One other tip: If tables are used, DO keep all table widths to a percentage. Any cell width numbers may wreck havoc on the gpsr display.