how to locate server down time. I located a website in a free website hosting server. I discovered that sometimes I am unable to open my website and that i cannot get any emails to that particular server. How to locate that down time and uptime of this server?

You need to have a view at monitoring systems like Zabbix. But I suggest you to create simple party script that will attempt to get the page periodically and log the end result. When you'll have daily statistic you can easily calculate which area of demands are fails.

This may be easily accompished with following command in party:

* * * * * curl http://server.com > /dev/null; echo $? > /var/log/connect.log

The calculate how mush the lines aren't equals to 0.

wc -l /var/log/connect.log; grep -cv 0 /var/log/connect.log

You will see two amounts. First is overall queries count, and 2nd is count of unsuccessful queries.