Css floats position?

I have read a few pages on this and feel like I am just not getting the concept. I usually pick stuff up with out much effort but floats hve me stumped. I want to move a group of text in the middle of the page. Well more so to the left middle. Now most float pages don’t say to use numbers while positioning things but use terms like right or left. That won’t work for me because I need the content aligned at a spot that cannot just be defined as ‘left’ I’m trying to place the content text over an image in my layout. Its a gradiant so I wanted the bg to stay in place and just have the content text scroll if needed. If you want to see what I mean u can check out the link below though the text is not positioned with a float and moves if you adjust the browser window. Can anyone help?? Http://www.lyonsdesign.info/about.html