If you take your laptop to the library to use, you will either have to take your laptop power source (cord) with you, or just run the laptop off of the battery. Every laptop you purchase comes with a power cord.
I have had Dells and HPs before--a few of each! I worked from home and away on the computer, so I've had quite a few in the last 20 years. The HPs had the best screens, but every HP I ever had but one (which was a huge laptop which was basically a tower crammed into a laptop) broke and had to be sent back, and broke and broke and broke until when the warranty was up and it broke again, I gave up and bought another laptop. Mostly what broke were the mechanical aspects of the laptop, like the power button and other functions at the top of the bottom part of the laptop.
After the third time with this, I switched to Dells. The only things I didn't like about the Dells are that they are heavy and run hot. Since I really do use my laptop "on my lap," this was a problem even with the buffer pad my husband bought for me. The Dell's battery lasted less than 2 hours. The HP batteries gave up the ghost soon after the one-year warranty gave out.
I am now using a solid state hard drive Toshiba,
Toshiba Portege Z935-ST4N01 Ultrabook which is light as a feather, runs very cool, and has the longest battery life of any laptop I've ever owned. Solid states usually don't have a built-in DVD player, but you can get an external player for $35 (not the $59 they show you on the Toshiba site I gave you).
They have a card reader for your camera's card, and a lighted keyboard. I think the screen resolution is great. You won't find a 17" screen, though. But picking it up and carrying it from lanai to living room to kitchen to front porch is a piece of cake
As far as the Yahoo problem you mentioned, that is probably because the settings in the Yahoo you saw on the laptop in the store were different than the settings for the Yahoo you are used to using at home.
I hope that answers some of your questions.