Html Problems

I have a little glitch on my blog that I haven't quite figured out how to fix. It has something to do with html I suppose, but I suck at it. So I hope some one can assist me with this:

I just changed my layout but now, I realise that for certain posts, my entry would be suspended in the middle of the blog and not appear at the top where it should be.

Thing is, I have plenty of links on the left column, so that makes the length of my blog rather long (which means alot of scrolling down). So for my shorter posts, which doesn't quite fill up the space, there would be an awfully huge white space at the top, before my post appears mid point. Not sure if I've explained it properly. But it's something like this: Example

I'm getting rather frustrated... but I think it could be solved with some simple html? But because I am bad at it, I'm in quite a fix. Anyone out there knows how to solve this? Would really appreciate it!