Various markup updates

Changed table-based nav to lists, added aria role attribute, added meta tags, removed unnecessary stylesheet attributes, hyperlinked logo image, removed transparent space from logo image (position using CSS instead), updated indentation, minor content update to remove "click here" text from link (UX best practice)
Merge pull request #1 from tedw/patch-1

Various markup updates
Merge pull request #2 from tedw/master

Remove transparent space from logo image, convert to jpg to reduce size