The structure of an HTML document can be seen as a document tree. The root is the html tag, and the two largest trunks are the head tag and the body tag. Offshoots of the head tag include the title, style, script, isindex, base, meta, and link tags. Offshoots of the body tag include:
Headings (h1, h2, and so on)
Block-level elements (p, div, form, and so on)
Inline elements (br, img, and so on)
Other element types
The objects with the same name, such as a group of options, are collapsed into an array. You can access a particular object in the array by incrementing the index with zero as the origin. For example, the first option with the name “myRadioGroup” inside a form called “myForm” is referenced as document.myForm.myRadioGroup.