Some minor details, that I feel can make a big difference.
Pretty Permalinks
Permanent links that help real people, not computer nerds navigate your site better. Many pages have long links that are cryptic even for geeks. They include %, ? and other nonsensical characters that only really make sense to the computer programmed to read them.
Speed
Especially when you live in 3rd world countries where bandwidth is limited and traffic is capped. This includes making sure files are small and compression is used where possible.
Clean CSS
Cascading Style Sheets can simply and effectively take an odinary looking site and transform it into a thing of beauty. Although getting your site looking just right can take up much needed beauty sleep.