When to file itr

Whenever any receipt from foreign country, reporting under AIR.............

Advisable to file nil return.......

Exemption limit for Assessment Year 2016-17 
You are exempted from income tax if your income does not exceed Rs 2.5 lakh. However, this exemption is only for individuals under 60 years of age.
If you are between ages 60 and 80, you are exempted from income tax with an income of up to Rs 3 lakh.

For individuals aged 80 years and above, the limit is enhanced to Rs 5 Lakh.

But no time is left. Do I have to file now or don't file it as the website is down?

No penalty even if you file Nil ITR of AY 2017-18 till 31.03.2018

What if I don't file ITR?

No penalty........ but  compliance to reply notice that may be received as per Non-filers Monitoring System of Income tax return.......

Refer: cbdt-identifies-67-54-lakh-income-tax-non-filers

and non-filing-of-income-tax-return-notice