Recently, I've been coding a lot on my 14" Dell Vostro Notebook, and I find it straining on my eyes.
I am planning on purchasing at least 23" Monitor, and I am having hard time deciding which one should I buy.
So please recommend which monitor should I buy, primarily for long hours coding.
First make sure you have a monitor with a quality panel - no TN. If its IPS or some S-PVA/P-MVA doesn't matter. Maybe take a look at different panels in a shop. I am personally very happy with my MVA-Panel monitor because of the good black levels. Try to avoid glare panels AND glare frames around the panel.
Next, make sure the monitor can be adjusted, not only in height but also tilt. I found that really useful adjusting the monitor to my seating position.
Regarding eye strain, the most common cause of this is setting the monitor backlight too high. Especially with LED backlights. Even in a normal lit room I only have set the backlight to around 10%. You may need to get adjusted to this first if you are used to normal settings (e.g. the default settings of the monitor which are always way too high), but for me it helped great deal with eye strain and headaches.