My question about document library web parts that appear in my first page in SharePoint 2010 Sites. (this picture )

when users want to browse in that web part and when they click on folders cant go up one level back!
how can i add button there to do this?
is there any hot key for this purpose?
what is your opinion or suggestions for solve this problem?
// EDIT
up one level icon button on the ribbon in library tab. and users cant find it