|A few things:|
1.) You have a header1 element in your document's head. They belong only in the document body.
2.) The header1 element is capitalized. All xHTML elements must be lowercase to abide by standards.
3.) The order of elements the header should be: Doctype, <html> (w/ xml and language defined), <head>, meta (define content type and character set), title, then all the rest of the header information.
4.) Right after the title, you opened a script element, but didn't close the opening tag.
6.) You never closed your document head.
7.) After the "Highest Watefalls" header1, you have text followed by a closing paragraph tag, but never opened the paragraph.
8.) If you use apostrophes to encase a section, you need to use quotes to encase a subsection. Example:
document.Write("<table><colgroup span='3' width='20%'");
9.) You didn't close the colgroup element.
10.) You have two closing script tags after your table.
That should keep you busy for a while. Clean up those and I or someone will take another look.