Move up narrowcolumn and Safari issue

Hello there,

I’ve been modifying my blog so it matches with my iWeb website. I just have two issues that i’m not able to resolve alone:

1) How could I move up from about 10px the narrowcolumn? The whole part where all the posts are is not at the same level from the sidebar. You can see this by watching the vertical rule between both of them. How could i repair this?
2) As i’ve switched to Safari, i discovered Safari. Everything works fine with except for the line under the post info and date. this horizontal rule is displayed one pixel above in Firefox and is perfect in Safari. If i change the value, it’s perfect in Firefox but not good in Safari…

Here’s my stylesheet: https://seriusdesign.free.fr/blog/wp-content/themes/arnoz/style.css
Here’s my website (under construction…): https://blog.arnoz.be