A website uses many technologies with varied setbacks, some of the technologies are from third parties and they are offered as they are (With or without setbacks because they are open source software) like the applications for the webmails ect.

Some of the setbacks are caused by the type of services.  Shared hosting for example have many problems because other clients problems can affect other innocent websites. For this case website functioning failure is expected anytime because of the third parties and shared services.

Also website problem rooted on website external attack.  When a website is attacked from outside like hacking, fake traffic flooding, may slow or make a website inactive or slow or malfunctioning etc.

Below a some of the common website crashes reasons:

Server Error

Your web host provider may be experiencing server failure either from the hardware, services like power or software that manage the server. Misconfiguration may also affect the performance of the server.  The server might be running a scheduled maintenance.  They might be experiencing severe attack etc

Massive Traffic Spike

The website traffic can abruptly go higher due to:

1. Fake traffic
2. Some of your posts, article are suddenly receiving a very high genuine traffic because it either went viral or

A website fake traffic is caused mainly by some software that can generate fake traffic to targeted websites. This traffic is sent as if visitors have visited your website and therefore the server traffic meter record the visits. Some fake traffic signal may even go further and initiate operations that will increase processes within the server resources and hence the website can crash at any time. It is difficult to block them since they keep changing the hostnames and methods.

If the website traffic went higher due to genuine visitors then you will ahve no other option but to upgrade the service to the desired traffic limit that suite the current needs

Hacking

Hacking occurs when some one from the remote computer access your admin area without your consent and take control of general website functionalities. Hacker can access your website using bots or manually and in both cases, the hacker can install software, change configuration and sometime delete your contents and put other content to the website. The hacker can use the website to steall visitors important data like those of credit cards and bank plus contacts like email and passwords.

1. VPS hosting
2. Semi dedicated hosting OR
3. Dedicated hosting.

These services will dramatically reduce the setbacks found in shared hosting environments

On our part we make sure that these failure will not interfere with the normal business processes. Bit as I pointed earlier, some of the problems need to be resolved at the endpoint of the customers, especially those related directly to the CMS scripts and webmail applications (third party services) and for this case the company need to have someone to do this either permanently or temporary on tasks bases.