You can do it so that when you switch from html to visual the iframe is still there, I have done this with the assistance of the plugin Max Banner Ads Pro on my website, you create a zone in widgets, then in options for that zone you tick single post/page. Then you add banner and the iframe text is copied into the Other Text Ads/Flash/Javascript (Adsense, Adbrite etc…) box and saved, then under the actions for that banner copy the post tag into your html editor wherever you want it on the page and will look something like this <!–MBA:Banner=7–> in the html when you switch to visual you see nothing but when you swith back, bingo it is still there. this saves yo from having to re copy the Iframe into to your page everytime you edit that page. ??
