The beautiful thing about iWeb is that it's one of the more fully-functional WYSIWYG ("whizzy-whig") editors out there, meaning that how you lay it out in the application is what it will look like in the browser, barring any browser inadequacies.
You can publish to a folder locally on your machine then open it in what ever browser you need to. IE often has issues with iWeb created sites though, but other browsers can have issues too including Firefox and Safari.