Image alignment

hi, im not sure if i posted this in the correct section
i have an image, and i want to position in in the center
i put it into a layer using dreamweaver, but have no idea how to align a layer to the center… i can align the image using a table though, but i find tables very complicated
i have tried setting the coordinates of the layer to look fine on my 1024x768 resolution screen, but if i try resizing the browser, the layer doesn’t stay at the same position, so i assume that the coordinates take alignment from the size of the browser only
wad i want is for the image to stay at the same position no matter wad screen resolution u are on, like if i set the alignment mode of a table to “center”, it will always stay in the center of the screen, but not for a layer…
somebody help pls?