I've have to develop my joomla understanding,so please Guide me what are must visit daily websites for joomla Designers? other then Stack OverFlow.

The only real factor I'd classify as must “visit” daily websites for joomla devs may be the weaknesses and extension weaknesses lists. Little else is day-important. But that might be fit more for website owners than devs.

For enhancing joomla understanding, don’t visit daily sites but develop and appearance the wiki. There’s guides there that may help you.