Question: Some time ago I've found a good online map for Alpine hiking trails. It was very similar to Google Maps and had green background.

I forgot the address and can't find it in google now. It wasn't myalps.net

Do you know this, or similar maps?

EDIT
----

I've found this map in bookmarks on my old computer:

<http://alpenkarte.eu/>

Nevertheless the maps recommended in answers are very useful too. Thanks!

P.S.: I've been searching google 2 hours and couldn't find ANY of them. It seems like google isn't very good at indexing map websites other that their own...

Answer: 
The Website <http://waymarkedtrails.org> shows sign posted hiking trails. The data comes from OpenStreetMap.org It shows the logo used on the signs and indicates the difficulty of the hike with different line styles.

And it features the requested green background.
Best Austria Alps maps are Kompass: 
<http://www.kompass.de/touren-und-regionen/touren/>

Switch layer to Summer/Winter in top right to see the details like marked trails and contours (otherwise it shows Open Street Map with less details). There are even winter ski tours there.