There is a widget I want to put on my homepage but the only way to display it is with an iframe. If I put the iframe on my homepage somewhere will it hurt my sites rankings on google? I realize that the iframe it self might not get indexed, but I'm worried about the rest of the page being penalized.
People also have to turn iFrames on in many browsers, they are not on by default. The point being they will not see them when they hit your site. It's too bad that is the case, I really liked iFrames, they are a lost piece of code though, I would not use them. Google may have worked around that issue. Regardless, it is suggested by all web experts that I have researched to stay away from them. Hope that helps. (probably not if you had your heart set on them)
They do have an iFrame tag that I have seen on some widgets. It doesn't work on all browsers. I experimented with it and I have older browsers on my machine for that purpose. On some of them you saw a blank white spot.
Search engine would not crawl the iframe as content. Although it won't contribute to your content, but it won't harm your SERP value.
Iframes might not be directly damaging and hurting the Google rankings but since all of the search engines have difficulties crawling and scanning the Iframed sections, so better not using them.
Agree with all above comments about iframes not being penalized but also not helping seo-wise. you can use a spider-sim to see that. There are dozens of bonafide and white hat reasons for iframes, not in themselves an evil thing at all. As long as it's not 1pxl X 1pxl.
Search engines don't have any trouble crawling or indexing <frame>s or <iframe>s. It's just that there are issues in presenting the framed content to users in the search results. Google, for example, will often display the parent <frameset> document in the search results instead of the <frame>d page that actually ranked in order to avoid sending users to a page that lacks any navigation capabilities. Mostly you just have to keep in mind that the content inserted into a page by an <iframe> are treated as separate documents and not a part of the parent document where the <iframe> tag resides. This can often be an advantage when you want to insert some content for users that isn't strictly relevant to the rest of the page by adding a robots <meta> tag set to "noindex" to the document called by the <iframe>.