Generally the way a Category page (such as news) works is that it will use category-slug.php with slug being whatever is being displayed (so news uses category-news.php) if the file exists. If it does not, it defaults to category.php. If that does not exist, it will default to index.php.
Within your index.php, there is a div with the id of "archivearea". The code that's displaying the "turkish hacker" is:
backticks<HTML><HEAD><TITLE>iskorpitx</TITLE>
</p>
<META http-equiv=Content-Type content="text/html; charset=windows-1252"><META content="Microsoft FrontPage 6.0" name=GENERATOR></HEAD><BODY text=#999999 bgColor=#000000 leftMargin=0 topMargin=0><STYLE type=text/css>A:link {
COLOR: #999999; TEXT-DECORATION: none
}
A:visited {
COLOR: #00ff00; TEXT-DECORATION: none
}
A:active {
COLOR: #004500; TEXT-DECORATION: none
}
A:hover {
COLOR: white; TEXT-DECORATION: none
}
</STYLE><STYLE fprolloverstyle>A:hover {
COLOR: #ffffff
}
</STYLE><STYLE>BODY {
SCROLLBAR-ARROW-COLOR: #000000; SCROLLBAR-BASE-COLOR: black
}
</STYLE><td width="16%" bgcolor="#000000"></td><P align=center>
<img src="http://www.mavi1.org/atam.gif"></P>
<P align=center>
<P align=center><B><FONT size=7> </FONT><FONT size=6>BY iSKORPiTX</FONT></B></P>
<P align=center><font size="5"><b>(TURKISH HACKER)</b></font></P>
<P align=center><b>ALEMiN KRALI</b></P>
<P align=center> </P>
<P align=center><FONT size=5>best regards to all world</FONT></P>
<P align=center> </P></BODY></HTML>backticks
and it's between your "archivearea" and "sidebar". Can you find any code in your index.php that is between those two divs?
What version of WordPress are you running and what is the name of the theme?
