Thin line appears when I hover on the featured image

Hello everyone,

I am really really new to WordPress and hoping to get some help.

I just started to develop my first site with Customizr 3.4.16

On my front page, on right side of the 1st featured image a thin line appears when I hover on the image. I tried everything, read old forum posts, tried deleting and reloading the pictures and made the pictures to specified size of 270×250

I have this problem when viewed on Safari 9.0 but no problem on Firefox. My website is https://www.volkansadventures.com/blog

I would really appreciate if anyone can help me to get rid of the thin line appears next to the picture when animated.