Hi Daniel,
Although Axure generates an HTML output for the prototype the tool does not provide direct HTML editing capabilities such as those in Dreamweaver, for example. The HTML and JS code that Axure generates is not intended to be customized, although you may be able to tweak it a little AFTER it has been generated. This means that you will have to apply the tweak each time you generate a new version of the prototype.
Best,
-Ezra
Disclaimer: I am not an employee of Axure nor am I compensated by the company in any way, shape or form. Rather, I have a vested interest In its continued development as an avid user of the application on a daily-basis. (disclaimer by Ari Feldman)