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This is the support site for Andrews & Arnold Ltd, a UK Internet provider. Information on these pages is generally for our customers but may be useful to others, enjoy!

FireBrick Custom CSS: Difference between revisions

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div.main, div.sidemenu div.menu a, div.topmenu, textarea
{
font-size: x -small
}
div.footer
{
padding: 2px 10px 1px
}
div.footer *
{
vertical-align: top
}
}
Note that there is no space after the dot in <code>div.main</code> etc. This is essential; adding white space at this point would alter the meaning - see [https://www.w3.org/TR/CSS22/selector.html CSS selectors].
 
'''Note:''' The above brief example is known to currently produce certain '''defects''' in the webpages’ layout: TheA verticalknown layoutminor of the text within the footerissue is slightly off. More seriously, this change has madethat the wholevertical layout of the ‘Graphs’objects pagewithin quitethe afooter mess,is soslightly further work to remedy this is neededoff.
 
At the time of writing, the shipping CSS in the Firebrick FB2500 was v1.45.001 Ximenes, and the standard <code>font-size:</code> value in use was keyword <code>small</code>. This could possibly change in future.
 
=== Using CSS @import ===
Completely separate 'print'- and 'screen' stylesheets can be maintained in separate .css files and these files can be conditionally included by reference in a master .css file using the CSS <code>@import</code> directive at the top of the file with a media-type qualifier within the directive ege.g. <code>@import 'my_fb_print.css' print;</code>. This qualified import form is concise compared with using thea <code>{ }</code> statement block qualifier and in theory might minimise the size of an initial CSS download, depending on the browser. A general disadvantage of <code>@import</code> is the latency introduced by additional http requests, some of which can not be parallelised, so this delay increases page rendering time, unless of course the CSS is already cached.
 
=== Pulling in multiple .css files ===
* Alternatively, depending on your chosen configuration options, you may be able to log in to the Firebrick’s command line even if you find the web UI unusable.
 
== Performance degradation with external websites ==
 
If your custom CSS is located on an external web server, try to ensure that the web server of your choice is well-configured and has excellent availability in order to avoid the possibility of introducing unpleasant delays in the responsiveness of the Firebrick's web UI. (Perhaps consider testing what effect unavailability has on the behaviour of your Firebrick's UI - your Firebrick firmware release could exhibit a delay in response before a timeout if the link to the web server is broken, and as regards visual appearance if the custom CSS can not be fetched, then it could use previously cached CSS or defaults.)
To avoid introducing delays in the responsiveness of the Firebrick's web UI, choose a well-configured web server. If you are the web master of your chosen server, review the cache-friendliness settings. (Topics: 'cacheability', 'cache-control', 'ETags'.) Getting cacheability settings wrong could in theory at least mean that your Firebrick might possibly be compelled to refetch the custom CSS repeatedly. A number of excellent web-based tools are available that will check and diagnose cacheability issues of a website. If you are using the Apache web server, see the <code>https.conf</code> or <code>.htaccess</code> documentation relating to cache control options. Set long timeouts for cacheability of all CSS files and make sure that the Firebrick is not forbidden from caching the downloaded CSS. Using inappropriate short cache lifetimes, even zero, or disabling caching altogether is a fairly common and heinous practice.
 
To avoid introducing delays in the responsiveness of the Firebrick's web UI, choose a well-configured web server. If you are the web master of your chosen server, review the web server’s cache-friendliness settings. (Topics: 'cacheability', 'cache-control', 'ETags'.) Getting cacheability settings wrong could in theory at least mean that your Firebrick might possibly be compelled to refetch the custom CSS repeatedly. A number of excellent web-based tools are available that willto check and diagnose cacheability issues of a website. If you are using the Apache web server, see the <code>https.conf</code> or <code>.htaccess</code> documentation relating to cache control options. SetMake longsure timeoutsthat foruser cacheabilityagents ofare allnot CSSforbidden filesfrom andcaching makedownloaded sureCSS thatfiles, theand Firebrickset islong notcache forbiddenvalidity fromtimes cachingfor theall downloadedCSS CSSfiles. Using inappropriate short cache lifetimes, even zero, or disabling caching altogether is a fairly common and heinous practice. Cache validity times should be set specifically according to each kind of file extension (<code>.css</code>) and MIME type requested (<code>text/css</code>), and should be as long as possible. The maximum validity time value is the maximum delay you feel is acceptable before a Firebrick shows the effects of a change when you change the css file on the web server.
 
== Security implications ==
To avoid having to use an external website to store your custom CSS, you can employ a <code>data:</code> URI - see [https://tools.ietf.org/html/rfc2397 RFC 2397]. Be aware that there may be a limit on the length of URIs however, and in any event see RFC 2397 section 2.
 
IIt recommendis recommended that you should not attempt to include newlines in the inline CSS of your data URI, as this may be forbidden by the URI scheme standard. Be aware of the risk of your inline CSS containing characters that are either prohibited in data URIs, illegal in quoted strings or in XML attributes. See both the RFC for the data URI scheme and also the XML standards. Just some examples of illegal characters are ", %, &, >, newlines and there are probably various others, The simple technique of including literal CSS straight, as below, is only usable if the particular fragment of CSS does not contain any problematic characters, otherwise see the next section for a general method.
 
Example,: straight, inline CSS. (exerciseExercise caution regarding prohibited characters if adapting). In the following example, any line-breaks maywhich be included for readability. These must be removed and the whole string must be entered as a single line.
 
<syntaxhighlight lang=xml><http css-url="data:text/css,@media screen{div.main,div.sidemenu div.menu a,div.topmenu,textarea{font-size:x-small}div.footer{padding:2px 10px 1px}div.footer *{vertical-align:top}}" />
</syntaxhighlight>
 
Note the presence of the comma after <code>text/css</code>. This is essential in a <code>data</data> URI.
 
=== Base64-encoded data ===
You may use base64-encoded <code>data</code> URIs for safety and complete flexibility as shown in the example below. Using base64-encoding removes any risks and problems with illegal characters completely. Note again the presence of the comma, now after the keyword 'base64<code>data</code>'. This is essential in a data URI, whether base64 is used or not.
 
If you are using any non-ASCII characters in your CSS text, unless you have already CSS backslash-hex-encoded them, which avoids the issue, your CSS should be Unicode text and you must first UTF-8-encode your CSS into a byte stream, before then base64-encoding those bytes. You ''must'' then also declare that your original CSS text was UTF-8 as in the example below.
<syntaxhighlight>
css-url="data:text/css;charset=UTF-8;base64,QG1lZGlhIHNjcmVlbntkaXYubWFpbixkaXYuc2lkZW1l
bnUgZGl2Lm1lbnUgYSxkaXYudG9wbWVudSx0ZXh0YXJlYXtmb250LXNpemU6eC1zbWFsbH1kaXYuZm9vdGVye3
bnUgZGl2Lm1lbnUgYSxkaXYudG9wbWVudSx0ZXh0YXJlYXtmb250LXNpemU6eC1zbWFsbH1kaXYuZm9vdGVye3BhZGR
BhZGRpbmc6MnB4IDEwcHggMXB4fWRpdi5mb290ZXIgKnt2ZXJ0aWNhbC1hbGlnbjp0b3B9fQ=="
pbmc6MnB4IDEwcHggMXB4fWRpdi5mb290ZXIgKnt2ZXJ0aWNhbC1hbGlnbjp0b3B9fQ=="
</syntaxhighlight>
 
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