Welcome to WebmasterWorld Guest from 18.104.22.168
Here are some starters.
1. Put some navigation links so you can get back to the page you were on without starting clear back at the beginning and having to click 6 times till you get back where you were.
2. Speed up the server so you don't have to wait 6 seconds for a page to load. I almost thought I must be back on an old 300 baud modem!
3. Do a little human proofreading of what people are putting in the different categories or at least allow users to flag them as inappropriate. As a scientist with a site oriented towards other scientists I can assure you my audience will be very interested in scientific equipment but that does not include 'Hunting Spot Lights' or 'Office grill light'!
This could be a great product with a little care but right now it is crap.