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Are you talking about a banner ad or just a banner on your site? If it is just a banner on your own site, I don't really see the harm and Google can't tell what is on the image. You should also contain the information in text on your contact page and possibly in the footer of your site. If you are talking about an ad that appears on other sites, I wouldn't recommend this. You are using up valuable ad space and more than likely someone isn't going to call you or jot down your address before they click on the banner and check out your site.

It's normal that when you make updates to your content the value of the page is changing and google recalculates it. Try to make changes only when necessary especially if you're editing: revenue delivering pages good ranking pages You can use the low traffic pages and not good rankings as a test to see what is most beneficial. Try to group all your changes and make them only if necessary. If you're doing that for freshness as I said before use articles or other pages which will gain new keywords, may be new links and build value there to flow to your listings pages. You don't want your listings to bounce up and down in serps.