Is it right to edit previous posts?

Occasionally when I'm looking back at previous posts I notice typos or mistakes. Or just stuff I wrote that sounds really lame. If it's a recent post I change it, but if it's from a while back, I feel wrong changing it, you know? Because I feel like I should preserve it - sort of... I won't write like that again. In fact, I won't even  change the font or colouring - and I know this sounds really stupid - but it's sort of for the same reason: I wrote it when I was younger and I feel like I'm faking it if I change it now. Because even if I edit it, it still comes up in the same order (As in, if you edit a post, it won't come up as the latest post) so it appears like I wrote like that a while ago. And I didn't. So it's like I'm lying. The problem is, sometimes the font or colour is Awful with a capital A.