Href back one directory

how do i link back out a folder using th a-href tag

Try setting your link to be your site root as so; note the / in front of home.html:

<a href="/home.html">bla</a>

Or if you know the path is definitely one directory down then just explicitly tell it to go down 1 directory; note the ../ in front of the home.html.

<a href="../home.html">bla</a>