First of all, what you are feeling is completely normal. I have been online meeting girls for the past 8 years off and on, until I found my girlfriend. Anyways, you can "what if" yourself into the next century. The only way to know is to go on the date.
There is nothing wrong when you're on a date, and it's not working out to say.
"Listen, you seem like a really awesome person, but I can tell we probably aren't going to get along. The reason is (insert). Be polite and just leave at that point.
The thing with online dating is being very direct about your intetions and what you want from her. This can be personality type, relationship type, interests, must haves, can't haves, etc.
I can tell you some serious horror stories. I've even posted some things about them on the forum. Girls posing as being hotter than they are, etc. Or some girls lying about other things. However, men do it too online. It's an honor system so take it as it comes.
GOOD LUCK ON YOUR DATE!
