Some Browsers Don’t Support iFrames,In an iFrame, Your website may have your content on it, with another website’s content, but the content can change anytime, to material that you may or may not approve of.Some problems like Costly even if blank.
Blocks page remianing onload that is unwanted,and not semantic
You cannot get CSS to co-operate between the IFrame and the parent page, unless you control the stylesheets themselves.As mentioned above it is true that-
We can't gain good performance using I Frame, Some search engines may have difficulties with the pages referenced within i Frames. How much this affects a site’s or page’s search ranking is not fully know.
My suggestion would be to simply using all other options first. Don’t just jump to the iFrame solution because it seems easy on the surface.
