firefox shifting banner 10 pixels

Strangely, IE is doing what I want

[ianevans]

Working on a new css grid design and noticed that firefox is shifting a javascript inserted skyscraper ad 10 pixels to the right (which I can tell since I've got a grid ruler image as the background while I design).

Everything else is aligning perfectly, and the floated div to the right of the div in question is perfect.

When I outline the blocks using the webmaster extension, the outline is sitting smack dab where it's supposed to be, it's just the ad banner that has shifted 10 pixels over to the right.

Padding and margins are 0. Here's the CSS:

#wrapper {width:965px;margin:41px auto;position: relative;overflow:hidden;background:#fff url(iangrid.png)}
#ad {height:92px;margin-top:5px}
#ba {width:180px;float:left;text-align:left;margin:0}
#main {width:600px;float:left;text-align:left;margin:0}
#sky {width:180px;float:left;text-align:left;margin-left:0}

ba, main and sky are inside wrapper. Funnily enough it's working as intended in IE7.

Any ideas?

[encyclo]

Hi ianevans, what doctype are you using, and what is the specific HTML you are using (ideally, the generated HTML from the JS)?