Not so fast...I'm not promising a listing, but that category sounds EXACTLY right. Are you doing web design and development? (check) Are the other sites in that general category offering web design services as opposed to information about web design? (check) Are you offering web design services related to real estate? (check) Are the OTHER sites in that category offering web design services -- again, as opposed to information about some aspect of web design? (check) And are you offering a unique good or service in that category? (check)
If you can answer all those questions "yes", and you can't find a more specific appropriate site, then that's the place. (What is it they say about the three most important real estate considerations?) And if the editor can answer all those questions "yes" by looking at the site and the category, then if there are no spam flags set off, there is a reasonable chance of a listing. [Here, "spam flags" might be things like "same webdesigning service has other single-product-line sites (fraternal mirrors)" or ... hmm.
Come back around the other way and look at the site, and the category you originally submitted. If a site is nappropriate for one category, an editor will normally look for a better category, or "punt" (that is, place it in a "misplaced" bin, so other editors who like to look for the right category, can take care of it.)
Obviously that's not what happened to your site. Why not? Well, I can't read the editor's mind, but I'll try to imagine borrowing his shoes for a moment. (Don't worry, I'll polish them before I put them back.) He's editing sites containing classified ads for real estate. He sees your site, claiming to build classified ads. He looks to see if there is actual content -- (that is, if you have ads as well as classifications: in fact, many submittals only have the classifications, and they expect us to promote their site so people will buy ads from them. That may be the most common reason for rejection in classified ads categories.)
What's going to happen? A site that SEEMS to fit the category, and yet has no content whatsoever: the light is on, but nobody's home. It fits a standard pattern of spam submittals in a moderately heavy spam target area. Where's that big red reject button when you need it?
Well, I don't know that's what happened. But I bet that's what WOULD have happened two times out of three if I'd been reviewing it.
Usual caveat: the level of detail (largely speculative) given here is intended to give insight into the ODP taxonomic thinking (in hopes that other lurkers can figure out how to find the best category for themselves. I know this concept is difficult: they try to drill it out of your head in Marketing 101. I've tried to explain it before, with something less than perfect success.) It can't be taken as a guarantee that any particular site will or won't be listed. But I can guarantee that the better your submittal fits the ODP mindset, the more likely it is to receive quick and/or positive reviews.