I visited some site and I noticed that the html its seem as encoded, like an hex character.
<meta name="description" content="הירשם/הי&#/>
What is this and what for?
how can I do this in my HTML also ?
It's not encryption. It's just HTML special symbols (entities). Here's a W3School page about that with their meaning.
Here's a site to decode and encode HTML entites. So this (הירשם/הי
) is meaning: הירשם/הי
.