Suppose we add in some pages a layer like:
<div id="Layer2">
<iframe src="somepage.htm" frameborder="0" width="aaa" height="aaa" scrolling="no"></iframe>
</div>

OR

<div id="Layer2">
<iframe src="somepage.php?a=b" frameborder="0" width="aaa" height="aaa" scrolling="no"></iframe>
</div>

If we add something like this to an existing page, will our rank be affected? Are the search engines (and google in particular) able to scan the content of the layer/iframe?
Will it affect our page rankings in any harmfull way?

Note: the iframe page will have a couple of flash banners or a couple of links. Both of them will point to other pages in our site.