If you are a web developer or programmer then you need to ensure that you are using best practises when working on client’s websites. If your client has asked you to make some major changes to their website, then you have a few options. You can of course make the changes straight on to the live site but this is often not recommended as if something goes wrong you may end up bringing your whole site offline. Also, if a customer visits your site whilst you are part way through the changes it may not display properly and make them leave. It could even mean that certain parts of the site wont load at all.
The best way to make changes on a site is to have a development test site that you can work on away from the main website. You can then check everything is working thoroughly before you swap it over on to the live site. You can also then allow your client to see a full working version of the site and check it over and make changes before it goes live to the rest of the world.
Be sure before uploading any changes to a live site that you have taken a recent back up copy that you can revert to should you need to.