Google’s bot and other search engine bots keep crawling your blog in a timely fashion. When, they see that your blog is offline in their visits, they start dropping your blog from the SERPs. The reason behind that is only a blog or a site can have rankings not a 404 page. Nobody wants a blog to be offline but it happens when you are upgrading your blog with some updates or when you are moving it to another server. There can be a lot of reasons for which it is necessary to turn your blog offline. But, when your blog is offline your blog starts to lose its rankings in a big way. All that efforts what you have been putting in your blog goes futile. When your site goes online again it might or might not be in the same place in the SERPs.
What is the solution?
The solution to this problem is to use a maintenance mode WordPress plugin.
This plugin makes sure that your blog is not offline even in the offline mode. Your blog readers get an offline message and so are the search engines. You can even set a progress bar or a timer which informs your readers that when the blog would be online again.