After i have checked all Problems with this, it works perfectly! The Code for htaccess musst be:
RewriteEngine On
#RewriteBase /
RewriteRule ^cat-(.*)-([0-9]+).htm categories.php?cat_id=$2&%{QUERY_STRING}
#Mod_bmollet : Image name in URL
RewriteRule ^img-(.*)-([0-9]+).htm details.php?image_id=$2&%{QUERY_STRING}
#Mod_bmollet : This is to make search function work ( redirect links from search results )
RewriteRule ^search\.htm$ search.php?%{QUERY_STRING}
RewriteRule ^search\.([0-9]+)\.htm$ search.php?page=$1&%{QUERY_STRING}
RewriteRule ^img([0-9]+)\.search.htm$ details.php?image_id=$1&%{QUERY_STRING}
RewriteRule ^cat\.htm$ categories.php?%{QUERY_STRING}
RewriteRule ^lightbox\.htm$ lightbox.php?%{QUERY_STRING}
RewriteRule ^img([0-9]+)\.lightbox.htm$ details.php?image_id=$1&%{QUERY_STRING}