Croatian/Serbian letters in CV problem

Don't forget to load fontenc with the T1 option; \DJ and \dj are not available in the default OT1 encoding. Add in your preamble:

\usepackage[T1]{fontenc}

Here's a little example, producing your letters:

\documentclass{scrartcl}
\usepackage[T1]{fontenc}
\usepackage{currvita}

\begin{document}

\v{s}\v{S}\DJ\dj\v{c}\v{C}\'c\'C\v{z}\v{Z}

\end{document}

Loading inputenc with the option utf8 (if your editor supports unicode), you'll be able to write some (and possibly all) of those letters, directly from the keyboard:

\documentclass{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{currvita}

\begin{document}

ćĆ

\end{document}

I don't know if this is possible for the remaining letters since I am not familiar with a "Croatian keyboard".

I do not speak nor write Croatian but here is how you type Serbian using TeX.

\documentclass{article}
\usepackage[OT2,T1]{fontenc}
\input{cyracc.def}
\newcommand\textcyr[1]{{\fontencoding{OT2}\fontfamily{wncyr}\selectfont #1}}
\begin{document}
Serbian alphabet again \dots \textcyr{\cyracc
A B V G D DJ E Zh Z I J K L LJ M N NJ O P R S T \'C U F Kh C Ch \Dzh\ Sh
} 
\end{document}

And the output is...

If you want to use Serbian keyboard (which I do not since I have been living in U.S. for the past 16 years) you will need inputenc package. If I recall correctly Babel assumes that you are using Serbian Cyrillic keyboard so it was not useful to me.

If you use XeTeX or LuaTeX, you can also use the fontspec package.

\documentclass[utf8]{article}
\usepackage{fontspec} 
\title{Mačak u vreći}
\author{Pero Perić}

\begin{document}
\maketitle

\section{Probni znakovi}
šđžčć ŠĐŽČĆ

\end{document}

I seem to be having less problems that way than trying to change inputenc and fontenc.