The html that is generated automatically for a page can't be changed without some fairly advanced scripting knowledge like javascript of Jquery. There isn't a place to change the html of a page.
There are ways to style, space, position, and color things in the existing html. That can be done with CSS. There are ways to add html to the page itself, by adding an html code box element and putting your html in that. The approach there only adds html to the page however, and doesn't rewrite the existing.
Hope this helps.
