Safari website

Your device does not have an option to do that out of the box. I'm sure if you jailbroke your device there might be a utility for that, but in any case.
Most mobile websites have an option to go to the "normal" version in your mobile browser (maybe at the bottom of the page).
It's up to you, but be forewarned - a lot of data may come from loading the normal (i.e. desktop-oriented) version of a website. A website has a mobile version for your convenience.

 

When a site detects a mobile browser such as Mobile Safari, it will send you to a mobile version of the site out of convenience for the user.

Usually, there is a link at the bottom of the page that says something like "Full Site" or "Normal Site" that you can click to return to the normal view.