First, let me say that I know this isn't true of everyone. It's my own prejudice, and I recognize it may cost me some good connections. I'm not judging any one person, or individual situations - just telling my side.
OK, now that that's out of the way...
Dating sites are all a little different, but one thing they have in common is the basics. They all ask you to complete a list of one-word answers, usually from a drop-down menu, to give an overview of who you are and what you want. Age, gender, city, occupation, sometimes birthday (or astrological sign) - and usually, your status.
By status, I mean are you single (as in, never been married), divorced, or widowed? Some sites, particularly those who also ask if you're looking for a relationship or just hook-ups, might even let you say you're "available" or even show your status as married. Yep, it's rare, but you do find people who are looking for casual sex and are upfront about the fact that they are married.
I (obviously) avoid people who say they're married. If "available" is an option, I usually avoid those people, too. Seems to me available means they are otherwise involved, but still looking for other options.
I stick to single, divorced, or widowed men. I generally don't start conversations with men who say they're separated. (I say generally because I don't rule it out completely, it just isn't my preference.) Separated suggests a few things, all of which are red flags to me.
One, you may have just ended your marriage - which means you're not in a mental place to have the kind of relationship I want. I can respect that; it takes time to recover from a marriage. I'm just not looking to sign up to be anyone's rebound.
Even if you think you are ready - you're not. Trust me, I know, I've been where you are. You'll find someone to help you through, I just don't want to be her.
If you didn't just end your marriage, but you are still separated, then I have to wonder why. Is your ex fighting you on something? Will there be drama? Are you not quite over her? Are you in a bad money situation? Are you just plain lazy or afraid to make decisions?
I was not separated and dating long. In fact, I only went on a few dates while I was still separated - and none of them were while my ex was sleeping on the sofa. As soon as I realized I truly wanted to date, I made arrangments to finalize the divorce. I had no drama, no custody issues, and I was not married to a jerk. I realize I was quite lucky - but even if you are not, where there's a will, there's a way.
If you really want to graduate from separated to divorced, you'll make it happen. If you don't - then you're probably not the guy for me.