I was chatting to a friend earlier about his website and what topic it should be on. His aim is to keep his site to a specific topic, I can see where he's coming with that, it would make it easier for people to know what they would find on your site. But I think trying to be too specific could also make it harder to easily post frequently. To keep interest in posting you would need a topic that you have a continued interest in.
With this site I would say you could sum it up as "Software Development" but I am sure other things will creep in over time. I'm not going to keep mine as strict since there are quite a few different things I want to try out in the future.
While chatting about this it reminded me about a website I had come across:
The person here had decided to try making a post every day for 30 days on a certain topic. In this case it was SQL Server DMV (Dynamic Management Views). the link about is the recap after the series was completed.
I think it's quite an interesting idea, though I would probably be tempted on planning out the topics ahead of time so I don't get half way though and realise I don't have enough things to do 30 days.