How do you manage server of your website ?

Managing server of your website is crucial. At initially after the launch of your website, there is a less possibilities of getting server errors but when time goes, you would upload more content and would get more traffic and it is necessary to keep an eye on this kind of errors. Errors like not found, Bandwidth limit exceed, redirection errors are seen commonly in websites. Sometimes you might use a different URL for managing promotion of your campaign and may generate custom URLs to manage and track and It is necessary to observe that each custom URL work correct.

So how do you manage this kind of errors and keep eye on these types of errors?