what is the date field in the registration form for?
by default it has todays date - if its a time stamp for finding out when the user registered there is no need to put the field there. generate the tim3e stamp on insert and insert it to the field use the date function.
url encode your get array elements
for example: hd=advertise%with%us in the _link_ would be hd=advertise+with+us
You have no _meta_ tags or keywords for the site as yet.
I am able to supply id values to the get array. it leads me back to the default listing which shows that your not checking if the id value does infact exist in the data_base_ before displaying. You'll want to put a check on that.
so if listing exist and is set to published where id value = to "whatever someone puts in manually in the url bar" then display else display a generic error page stating that the property listing they are trying to access doesn't exist.
The the good side of things though
unique page _title_s for all pages
welcome email, email activation, captcha to ward off spammers
Hope this help. Congratulations on completing your web project.