Can you make vibration of mobile stronger or longer?

I wonder If I can make the vibration of my phone stronger or longer, because sometimes I don't feel it when I get a sms.

Stronger - no.
Longer - you can apply pacth for using another tone for SMS alert. If the tone is long, the vibration will be long too.

This depends on your phone...

there excists ringtones with the extention .IMY they can let your phone vibrate as long as it rings. it can't set it stronger tho