You can have these rules like this:
RewriteEngine On
RewriteRule ^user/strategies$ /user/index.html [NC,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^user/([a-zA-Z_0-9.]+)$ /user/index.html?username=$1 [NC,L]
.htaccess
is per directory directive and Apache strips the current directory path (thus leading slash) fromRewriteRule
URI pattern.