keeping div boxes in the same place, i need some help Options

[rewop]

all my codes after a some amount of time alter so that all the boxes move up, to the left; or out of position. also it tends to look different on other people's computers.

could it be that i am defining positions with percents?

here's an example of one code

CODE

.div1 {
background-color:black; color:white;
border:2px solid; border-color:silver;
width:789px; height:1000px; overflow:inherit;
position:absolute; z-index:2; left:50%; top:0%;
margin-left:-394px; margin-top:150px; text-align:center;
visibility:visible;}
marquee { z-index:8; }

[rewop]

also everymovement seems to be centered around the higher of the divs
example

.friends {
blablblblhalbhlbah
blahblhablhblahblh
l;abhlahblahblhblh
blhablkhh

.comments {
lkdalksjdlskajlkjlvkj
asdlkjasldkjaslkdj;al
slkdja;lskjdklsajd;lj
sdsdasdsd

if i correct the 'friends' div then the other one goes back to its spot too. another thing that kinda puzzled me..