Fix/improve several things about generic template

[tripu]

…based on feedback last week:

• Make sidebars narrower (~20% of width?); if necessary, show them on wider screens only
• Reduce size of headings on sidebars (to emphasise they're secondary)
• Test on Konqueror (fixed stuff ain't fixed?)
• Review margins/paddings above headings; are they consistent?
• Don't make the footer stick to the bottom
• Add comment(s) on source markup pointing to this project, howto, etc