reccommended way to output HTML from JavaScript

I know this has probably been asked before, but here goes: I have a web application that needs to generate modal dialogs. alert, confirm, and prompt are too simple and ugly, and that modal window function...it's a long story. I can't use it. So, I'm going to create the modal box using DOM functions and CSS. However, I need to put quite a lot of content into the dialog, and I'm wondering what the best way to do this is. Putting the HTML into a string and using innerHTML is unwieldy. I could use the DOM, but that's annoying and takes too much time to code. I know I can use a script with a weird type tag (something like x-random/x-htmlstuff) and then copy it's content to the innerHTML, but is there a better, more "official" way to do this?