What's the code to link to a higher folder in HTML?

[Denair Cowboy]

Say for instance i have a webpage in folder "a" how do i put a link on that page to a file in the folder that folder "a" is in. in other words tell it to-Go up one folder and then find the file?

[Rajiv Vishwa]

where folder 'a' is inside the folder 'b' and 'file.jpg' is inside 'a'b>a and b>file.jpg