This plugin is used for displaying thin vertical lines at each indentation level for code indented with spaces. For code indented with tabs, I think there is no need to support it, using :set list lcs=tab:\|\ (here is a space) can achieve it.
This plugin takes advantage of newly provided conceal feature in Vim 7.3, so Vim 7.3 with conceal feature is needed.
To install the plugin just put plugin files in your ~/.vim (linux) or ~/vimfiles (Windows).
Setting custom line colors
For gvim, hi Conceal guifg=(color you like) guibg=NONE
For vim, hi Conceal ctermfg=(color you like) ctermbg=NONE
You can change indentline char by youself. change this variable: let g:indentLine_char = 'c' 'c' can be any ascii character you like, you can also use '¦', '┆' to display more beautiful lines, but this only aplies to file whose encoding is utf-8