Web site owners often add videos and other content from external sources to their web pages to increase keyword density and engage visitors.
From an SEO point of view this can often be a waste of time because often the content is contained in what is called an iframe. This is particularly true of Youtube videos.
An iframe (inline frame) is an external element embedded inside an html page on a website. The iframe html element is often used to insert content from other web sites, such as Youtube videos, advertisements, into a Web page.
Here’s an example of a page that has another page embedded in it using an iframe: http://btcnews.com.au/keiser-report-bitcoin.html
The trouble with iframes is the search engines do not attribute anything within the iframe to the web page that has the code embedded. The content is attributed to the web page that the content is pulled from.
A few years ago I did some work for a travel booking company. They told me they had created all this great content for their web site, but they still were not ranking, even for low competition keywords.
I went to their web site and had a peek and sure enough it was full of great images and copy about their various travel packages. When I had a closer look at the code I saw that the stuff they had written was pulled from one of those travel booking engines and presented via iframes.
In other words Google attributed the content to the booking engine, not to the web site displaying it. And to add insult to injury, the booking engine had blocked the Google spiders.
If you are going to use iframes for things like Youtube videos, it’s a good SEO practice to add some content on the page outside the iframe that describes the content within the iframe.