Generally, update modules on the websiteor some of the information can affect the entire code of the project. The pages may be skewed in some way "fail." Users who at this moment will be on the websitewill introduce to the system additional download. This can greatly affect the whole project. To protect yourself from such situations you need to switch off the website when you update information, or any other repair work.
If you are on the websitee is the engine, then it certainly has a built-in feature that allows you to disable the resource. This means that all information remains just users will not be able to get on the main page. Will be included automatically redirect to a html page with text about what the website is. Go to control panel project.
For this you need to login under the administrator account. Go to the tab "Settings" or "Control system". In different engines these menu options are called in different ways. Next, find something like "Disable websitea" or "Message when updating". Check the box next to "Disable site for a while." In this case, you can write the text that users will see when you get to the main page of the website.
It is also worth noting that make the website inaccessible when you disable the hosting. Almost all of these services offer the option to disable the resource when updating the system. Go to the website, which hosting do you use for your project. Log in and go to settings. Then just set to disable the hosting for your project for a while.