When a CSS link appears at the top of the page, preceding the </head> element, a browser can progressively render the page to quickly display the content, especially beneficial for users who access content-rich pages by means of slower Internet connections.
If a client requests an HTML document for which the response header contains a Cache-Control: private, Cache-Control: no-store, or Vary: User-Agent header, the BIG-IP® system removes the inline content from the response, and caches the inline content.
When you use inlining functionality, the following conventions provide best results.
For each user-defined policy, you can specify lists of JS URLs and lists of CSS URLs for concatenation. Listings in each URL list appear in the specified order.
During the process of concatenation, the first JS and CSS URL within the HTML file that is specified in a JS or CSS URL list is replaced with the optimized URL, and each subsequent specified JS and CSS URL is removed. The TTL of a concatenated response is determined by the earliest expiration of the concatenated objects.
DNS prefetching improves page load time on HTML5 compliant browsers by resolving domain names to an IP address prior to a browser requesting content from third parties. When DNS pre-fetching headers are inserted by the BIG-IP® system, HTML5-compliant browsers can do DNS resolution of dynamic links in the background while other items are being downloaded. This feature allows users to configure lists of DNS prefetch domains by inserting the following link tag in the head of an HTML document:
<link rel="dns-prefetch" href="http://www.siterequest.com// ">
By default, DNS prefetching is always turned off for pages served in HTTPS to avoid leaking information about which particular document is served. Turning on Force Injection on HTTPS enables DNS prefetching specifically for the domains listed in a domain list. Turning on HTTPS Automatic Page Prefetch turns on DNS prefetching for the entire document served. Force Injection on HTTPS must be enabled in order to enable HTTPS Automatic Page Prefetch. Administrators are able to configure turning on and off DNS prefetching when serving over an HTTPS connection by inserting the following head tag:
<meta http-equiv="x-dns-prefetch-control" content="on">