This is the default vBulletin 5 .htaccess file.

<IfModule mod_rewrite.c>
    RewriteEngine On

    #In some cases where you have other mod_rewrite rules, you may need to comment out the following line
    #and change it to match your folder name. This resets the other mod_rewrite rules for just this directory
    #If your site was www.example.com/forum, the setting would be /forum/
    #RewriteBase /

    # Send css calls directly to the correct file VBV-7807
    RewriteRule ^css.php$ core/css.php [NC,L]

    # Redirect old install path to core.
    RewriteRule ^install/ core/install/ [NC,L]

    # Main Redirect
    RewriteCond %{REQUEST_URI} !\.(gif|jpg|jpeg|png|css)$
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ index.php?routestring=$1 [L,QSA]

    # Because admincp is an actual directory.
    RewriteRule ^(admincp/)$ index.php?routestring=$1 [L,QSA]


<IfModule mod_expires.c>
    ExpiresActive On
    ExpiresByType application/x-javascript A1209600
    ExpiresByType text/javascript A1209600
    ExpiresByType application/javascript A1209600
    ExpiresByType text/css A31536000
    ExpiresByType image/x-icon A2592000
    ExpiresByType image/icon A2592000
    ExpiresByType application/x-ico A2592000
    ExpiresByType application/ico A2592000
    ExpiresByType image/gif A2592000
    ExpiresByType image/jpeg A1209600
    ExpiresByType image/jpg A1209600
    ExpiresByType image/png A1209600
    ExpiresByType application/x-shockwave-flash A1209600
    ExpiresByType font/ttf A2592000
    ExpiresByType font/otf A2592000
    ExpiresByType font/x-woff A2592000
    ExpiresByType image/svg+xml A2592000
    ExpiresByType font/truetype A2592000
    ExpiresByType font/opentype A2592000
    ExpiresByType application/x-font-woff A2592000
    ExpiresByType application/vnd.ms-fontobject A2592000

<IfModule mod_headers.c>
    Header set Connection keep-alive
    <filesmatch "\.(ico|flv|gif|swf|eot|woff|otf|ttf|svg)$">
        Header set Cache-Control "max-age=2592000, public"
    <filesmatch "\.(jpg|jpeg|png)$">
        Header set Cache-Control "max-age=1209600, public"
    <filesmatch "\.(eot|woff|otf|ttf|svg)$">
        Header set Cache-Control "max-age=2592000, public"
    # css and js should use private for proxy caching https://developers.google.com/speed/docs/best-practices/caching#LeverageProxyCaching
    <filesmatch "\.(css)$">
        Header set Cache-Control "max-age=31536000, private"
    <filesmatch "\.(js)$">
        Header set Cache-Control "max-age=1209600, private"