Random ordered listings - effect on search rankings?

[mcsalty]

I'm developing a website that consists of paid and unpaid listings in a certain business (for sake of example, let's say real estate). The paid listings will be displayed above the unpaid listings.

However, since all paid listings are charged at the same price, I'm trying to think of a fair way to order them such that certain clients aren't given arbitrary priority over others (like if I were to order them alphabetically). I decided the fairest way to take care of this would be to have the listings pulled in a random order from the database.

From a client's perspective, I feel this is the ideal solution, but I'm concerned with its potential effect on search results. If the website's homepage, which simply consists of pictures of and links to the various listings, changes every time the page refreshes, would google view this as some sort of blackhat attempt to fool search engines into thinking the site was more frequently updated? Could this have other random, undesirable results on search engine rankings?

I wanted to get the feedback of those who know more about search engines than I do before I launch the website. The other option would be to have the homepage regenerated every, say, 30 minutes, with the listings in a random order, but that would require more coding. Again, the only reason I'm designing the site this way is to be as fair as possible to my clients. If anyone has any other ideas regarding how to order the listings fairly, I'd be happy to hear suggestions.

Thanks!

[mark_roach]

I do something pretty similar on my site and those internal pages seem to rank ok, my home page is static though.

I have played around with how frequently I vary the order of the listings on many occasions. I am currently settled on rotating the list every three days. I have in the past changed the order with every refresh of the page and also used a single day and a 7 day cycle. I have settled on looking to balance giving the SEs and visitors a consistent page whilst still giving every one a fair chance of being top.

I wouldn't rotate the listing with every refresh as this can be confusing to your visitors. They may be working their way through each of your links in turn, hit refresh for some reason and then be faced with a completely different looking page.

I have more questions than answers as to whether it is a good thing to do as far as the search engines are concerned (I am sure it doesn't help, but how much the rotation hinders I don't know). However for me it is the right thing to do for my customers.

[mcsalty]

Thanks for the reply. Good point re: the user experience. I guess I'll probably end up rotating the listings once per day.

You don't happen to use Wordpress for your site, do you? I can't seem to find a plugin that takes care of it, so I figured I'd check before I spend the time coding something up on my own. I'm thinking of taking (number of the day of the year) MOD (number of listings) and cycling through the posts starting there. Have you thought of a better solution?

[mark_roach]

Sorry not a WP site.

I order my lists randomly and use the day number as the seed to the random function. This ensures for a given day the random number sequence is always the same and therefore the list is returned in the same order. I also use a couple of other factors (multipliers) which are used to determine the final order of the list.