Where should I write html in vaadin?
The idea with Vaadin is that you don’t have to write any HTML or JavaScript. In most applications you’ll be fine with the layouts provided with Vaadin (such as Horizontal-, Vertical- and GridLayout) or perhaps some of the layouts in the incubator (FastLayouts). Sometimes you might be required to create custom widgets (see Book of Vaadin for more information).
Sometimes you do run into cases where you need to write the HTML yourself, in those cases you can use the CustomLayout -component.
And of course, to display a small html formatted text snippets use the Label component in XHML or RAW mode.
See:
http://vaadin.com/api/com/vaadin/ui/Label.html