When you begin to look for a company to host your website, other than the amount of space and bandwidth that is offered, a company will usually promote the web hosting uptime they offer. Most web hosting companies like 1and1 , pickaweb, uk2.net offer an uptime guarantee to promote how well their service is. Other web hosting companies encourage their services by offering uptime assurance.

Web hosting uptime is a measurement of the time a computer server has been running, the longer the web hosting uptime the better the service (usually). Uptime is important to not only web hosting companies, but to any person or company that has a website, because if a website is down it could affect both your personal company’s reputation and goodwill of the web hosting uptime guarantee respectively. Web hosting companies strive for a 99.9% uptime, which means that there would be less than 2 minutes of downtime a day.

There are some factors that have huge impact on the uptime of a web provider, and rarely they are unavoidable. But good and reliable hosting companies try to prevent the downtime. Downtime is caused due to following reasons :
1) when the provider upgrades his server, or server is updated.
2) when some software companies put patch on the place of any fall foul of security.
3) when server is overloaded or any problem occurs in the performance of hardware or software or due to any nasty software.

Some temporary conclusions to resolve downtimes are:
1) Many web hosting companies provide friendly downtime message that will still allow the user know that the site is only temporarily down.
2) Larger web hosting companies are able to provide a quicker return to maintain their uptime guarantee, because they have staff readily available to respond to a downtime error quickly.
3) Smaller companies may experience a longer downtime. Because of lack of number of technical staff.

For reducing the risk of downtime, you can avoid purchasing the package from web host that has a lot of downtimes. You can go through forums and websites that keep the current record and reviews of almost all the hosting companies, where you can find their rating, their services and uptime they provide, and you can decide well before choosing any provider.
OR
You may choose webhost who cover the risk of downtime by compensating you with (1-Month Free Web Hosting added to your account) if ever you face downtime of (90+ minutes in total)monthly. Or credit the amount of downtime to your next month’s hosting fees.

In order to receive your web hosting service credit you must:

a) Email the details of the downtime to their support department
b) And as soon as your downtime is verified, your account will be addded with 1month free hosting or adjustment of hosting fees in the next month.

But if you have already hosted your site and you are facing the problem of large downtimes, you can contact to technical support or to any customer service unit. They will check and give you information that when your site will be restored. Many other web hosting companies provide with the compensation But make it clear that not a single company provides 100% uptime guarantee and if you are facing great downtime problems then the only way is you can transfer your site to some other established and reliable company.

So, go ahead and choose a Reliable webhost.