what are the elements of building a good classified website?

[Aziz]

im seeking any reference explaining about all elements of building a good classified website ?
ur help is higly appreciated

thanks

[hardy]

1.Charge for featured listings.
2.Spam filter and detector.
3.Quick posting and editing like Craigslist.
4.Ad Comments and Ad Ratings
5.Automated "bad words" checking
6.Better & more Flexible Search Engine. Can search on custom fields, as well
7.Better "View Details" and "Print details" as well as other items' descriptions output - thanks to the templates & items attributes system
8.Improved Images Uploading Mechanism: more flexible with automated resizing
9.Full pagination in the ads' listings
10.Compactness
11.Possibility to set the ad's duration separately for any category
12.Anti-Spamming: IP logging and limiting the # of sent e-mails of those who "send the ads to friends", who e-mail to the advertisers through an online form
13.IP Ban
14.Maximum automation. Minimum administration is needed though you may do a full administration from the admin panel
15.Security: image verification (CAPTCHA), protection from cross-site scripting (e.g. javascript code injections), email injection. Protection from file upload attacks. Secure persistent login implementation. Brute force login attempts rejecton. Admin Area file renaming is supported for security purposes. "Bad words" warning. Checks the validity of e-mail addresses entered by each user.
16.Already supported payment processors: 2checkout.com, paypal, authorize.net, alertpay, securepay.com, ccbill, innovativegateway.com. Other payment processors can also be applied.