Web site Usability
Take the worst first
All sites have usability problems!
All organizations have limited resources to devote to fixing usability problems.
You will always have more problems than resources to fix.
It's easy to get distracted by less serious problems that are easier to solve, which means the worst ones persist.
You must focus ruthlessly on only the most serious problems.
How to determine severity?
Will lots of people experience the problem?
Will it cause a serious problem for the people who experience it or is it just an inconvenience?
Determing severity is always a judgement call. The toughest problems are corner case (very bad problems for only a few users) and ubiquitous nuisances (affect lots of people but are only minor annoyances).
When fixing problems, try to do the least you can do
What is the smallest change you can make to prevent the problem?
Always tweak your site, improve the usability one change at a time. Tweaks costs less and require less work. Tweaks don't ruin lives, carerrs, or families. Small changes are quicker and more likely to happen.
If you make larger changes, you are more likely to break other things.
Most people do not like change. Tweaks are less obvious than redesigns. Redesigns annoy. Redesigns involve a lot of people in a lot of meetings.
Always relate everything back to a ROI.