Well, to "disconnect" your cell from relative positioning, you'll need to enclose it in an HTML element and modify some styles. As an example, let's say you are modifying the "Current Time" cell in the default layout. The HTML of this cell is:
<nobr>Current Time</nobr><br><currenttime showSeconds="t">
Change it to:
<div style="position: absolute; left: 100px; top: 100px"><nobr>Current Time</nobr><br><currenttime showSeconds="t"></div>
The left and top style attributes set the element's position, relative to the top-left corner being 0, 0. This will take some tweaking to get right. For example, while the font type and size are the same as those set in the cell's properties, the cell's background color isn't. You'll have to set that style attribute in the <div> element yourself (font attributes are inherited in HTML, but background colors are not). Also, you'll notice a very small space likely remains where the cell would normally display. You might have to group cells you position in this manner so as to minimize unintentional space like that. You'll very likely find some other peculiarities you'll have to work around.
