I don't like the logic behind the \rightmark for \subsection in this example.
\documentclass[12pt,a4paper]{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{xcolor,blindtext}
\usepackage[komastyle,nouppercase]{scrpage2}
\clearscrheadfoot
\pagestyle{scrheadings}
\automark[subsection]{section} % section left, subsection right
\setheadsepline{.2pt}[\color{black}]
\renewcommand*{\headfont}{\normalfont}
\ihead{\leftmark\ifstr{\leftmark}{\rightmark}{}{:}} % left: leftmark, and if rightmark differs, add an ":"
\ohead{\ifstr{\leftmark}{\rightmark}{}{\rightmark}} % only rightmark, if leftmark is different
\cfoot{\pagemark} % foot page number
\renewcommand*{\sectionmarkformat}{} % removes numbering from section in head
\renewcommand*{\subsectionmarkformat}{} % removes numbering from subsection in head
\begin{document}
\section{Intro}
\blindtext[8]
\subsection{Part of Intro}
\blindtext[2]
\subsection{next Part of Intro}
\blindtext[5]
\section{Outro}
\blindtext
\end{document}
I would like to see the subsection of page two in the header of page three, and not subsection 1.2 which starts at the same page. Imagine you flip the page and forgot which subsection it was: than it would be better if you can rely on the header. But the usual appearance shows you the same subsection you are also able to read in the center of page three.
So is there a possibility to change this behaviour, so that I can see the subsection (and the same for section, subsubsection ...) of the topmost text lines at each page?
I hope I expressed clearly enough. Thanks in advance!

\renewcommandthe\subsectioncommand so, that at its writing something like\markright{\lastsubsectionname}\section{#1}? – Phil Jan 06 '16 at 14:19\ifstrblocks subsections if a new section appears – Phil Jan 06 '16 at 14:21\subsection{Last Part of Intro}just before\section{Outro}in your example ... Then the first mark on that page is set by the\subsectionand not by the\sectioncommand. See also http://tex.stackexchange.com/a/280954/43317 – esdd Jan 06 '16 at 14:28\newpagebefore a sectioning command. It is really not easy to do this automatically, (without an explicit marking of the end of a section or subsection.) – Ulrike Fischer Jan 06 '16 at 14:38scrlayer-scrpagewhich adds\righttopmarkwhere\topmarkgives the mark last used on the previous side and the word right before forces it to use just the\rightmark, in my case this stands forsubsection. Now I only need to let\rightmarkdetect whether there is a\subsubsectionafter a\subsectionso that this will be prompted instead. Got my Problem? Any idea? – Phil Feb 04 '16 at 10:04