bogdan

Embeds are needed to embed video from youtube or to embed Google Map or just to embed content from external page. 
WordPress removes embed when you switch from “HTML” to “Visual” tab because of the security reasons. 
So you can embed object code using this shortcode <code>[iframe src="http://player.vimeo.com/video/3261363" width="100%" height="480"]</code>.

iframe to embed

Embeds are needed to embed video from youtube or to embed Google Map or just to embed content from external page.

dbhynds

Lazy load images, YouTube and Vimeo videos, and iframes using <a href="https://github.com/ressio/lazy-load-xt" rel="nofollow ugc">Lazy Load XT</a>.
Lazy Load XT is the fastest, lightest, fully customizable lazy load plugin in the WordPress Plugin Directory.
This plugin works by loading the Lazy Load XT script and replacing the <code>src</code> attributes with <code>data-src</code> when the content of a post or page is loaded on the front end of a WordPress site.

Lazy Load XT

See this image
http://i.imgur.com/PzOIDGI.png
It's my main page's slider, it loads blank when installing this plugin
When the page loads at the first time without any cache, it loads with the browser's default font, then suddenly changed into the site's font. Not just the images in "not seen parts", but also images in the view port load blank. I would say this plugin has a huge potential, but at the moment, as it's not updated, it doesn't function as it advertises despite having 5/5 reviews.



Not really impressive as I thought

Lazy Load images, videos, iframes and more using Lazy Load XT.

iframe to embed vs Lazy Load XT