is it normal my macbook air gets slight hot in the upper left part in normal browsing and usage?

Warm or even hot may be ok, but if it's so hot you're concerned something is wrong you might want to have that Mac evaluated: Contact Support. No exterior surface should ever become so hot it becomes painful to touch or even hold for a prolonged period of time.

If your Mac has a MagSafe power port, read Apple Portables: Troubleshooting MagSafe adapters. Periodic inspection and cleaning is a requirement: Step 8.

To add to @John Galt's excellent advice the fan is located in that area along with part of the CPU heatsink so it will be hotter in that precise location compared to the right side.