A article at Web Hosting Geeks (a web hosting Reviews, Rating and Awards provider) “Why Reliable Web Hosting?” has some good valid point on Reliable web hosting. Your web host will be termed under reliable when,
- Server monitoring with 24×7 security safeguard is beefed-up for your site
- Top of the class spam and virus filtering system to safeguard your e-mail IDs
- Daily site backups are taken with top priority
- Firewall protection from unwanted activities
- Guaranteed 99.99% uptime
As per the article:
Reliable web servers with multiple fast connections are critical in ensuring that your web site runs smoothly. Only behind the hosting company’s firewall and additional security on their web servers can you seek to keep your website safe from unwelcome intruders. Spam and virus filtering is another essential feature which should be taken into account with all email facilities. This is again possible with only reliable web hosting.
Being blogger I understand the need and necessities of reliable web host. Previously when my blog was on different server rather than my current server(ANHosting), I found server down for several times and that was scared moment for me. Because I’m loosing my readers attention.
So, whenever you choose web host give first most priority to the above points and never go to lucrative cheap plans. If your server is down for several times, then what is the need for huge space, huge bandwidth… etc. 
