I am working on a project for school and wanted to use the less library. I tried something like
<link rel="stylesheet/less" type="text/css" href="style.less">
but this didn't work, I got the error
XMLHttpRequest cannot load file:/// [..] /style.less. Cross origin requests are only supported for HTTP.
Meaning I basically need to run a server for this implementation. However, since this is supposed to be a stand-alone project for a non-technical class, running a server is out of the question. So, my question is:
How do I use less at document level, the same way one would write the css equivalent
<style>div{color:#F00}</style>?
Searching the google for "document level less" returned no related results.
You can't use LESS at document level. Less is a pre compiler for CSS, so you should use the end product in your site (css). You don't need a webserver to show html + css local in a webbrowser. You can compile your LESS to CSS client side (by including less.js) or server side, the source code bundles a compiler.
Also read: Is there a way to bypass Javascript / jQuery's same origin policy for local access?
for example the file like below works also when i load it from my local files in a webbrowser:
<html>
<head>
<link rel="stylesheet" media="(max-width: 767px)" href="green.less" />
<link rel="stylesheet" media="(min-width: 768px)" href="red.less" />
<script type="text/javascript">less = { env: 'development' };</script>
<script src="less.js" type="text/javascript"></script>
</head>
<body>
<p>color this text</p>
</body>
</html>
update
When you are sure javascript works and less.js loads and you don't see your styles still, their probably will be an error or typo in your LESS files. If there is an error, your LESS file won't compile, so their will be any CSS and you won't see any styling.
By default less.js don't show errors in the browser. Add <script type="text/javascript">less = { env: 'development' };</script> to your source to allow LESS errors shown in your browser (from: https://stackoverflow.com/a/11289000/1596547).
Example:
Related
I have a simple, local HTML file:
<html>
<head>
<link href="stylesheet.css" rel="stylesheet" type="text/css"/>
</head>
<body>
<div class="myclass">Hello World</div>
</body>
</html>
and a simple stylesheet:
.myclass {
color: #456123;
background-color: red;
}
I am deploying my stylesheet to an outside cloud hosting service (AWS S3). However, when I swap the URL out, the styles don't work anymore:
<link href="https://example.s3.us-east-2.amazonaws.com/stylesheet.css" rel="stylesheet" type="text/css"/>
What do I mean by they don't work? The page doesn't display correctly, none of my styles get applied. The page renders as if there was no stylesheet at all.
I've tested all the obvious things, and then some:
The remote stylesheet is accessible, I downloaded it separately by URL and WGet
The remote stylesheet is the exact same as local, byte-for-byte (no diff)
I have disabled cache in my browser
I have hard refreshed
Per my browser tools > network tab, the browser loads the stylesheet promptly (~200ms)
Per my browser tools > sources tab, I can confirm that the entire stylesheet is there, present as a source and readable
I even wrote a script that I loaded into the body that fetched the CSS stylesheet externally, and using a callback after that, created the myclass div. The styles still didn't apply, even when controlling for latency/race conditions like that.
What could be going on here?
Fixed it! I found a similar problem here, which led me to the answer: when CSS files get uploaded to AWS, they get uploaded as Content-Type: Binary/Octet-Stream for some godforsaken reason. (Madness!)
My browser tools didn't raise that as an issue -- I guess browsers are pretty flexible these days -- but it must've still been an issue for HTML rendering.
So the solution is simple: go into AWS S3, click on the file, and change its metadata to hold:Content-Type: text/css. Or you can also set that metadata programmatically if you're uploading these files via an AWS CLI or SDK.
As an aside, you should do the same for JS files, which also get uploaded as binary/octet-stream. For whatever reason, the browser is still able to execute those fine.
i am trying to reduce my webpage load time . When i am searching i come to this point preload css and javascript .
So i am trying to implement this in my html page please see my html code before and after implementation
before
<html>
<head>
<link href="http://fonts.googleapis.com/css?family=lato:400,100,200,300,500%7COpen+Sans:400,300,600,700,800%7COswald:300,400,700" rel="stylesheet" type="text/css"> ...........
</head>
<body>
html contents
<script src="assets/js/jquery-1.12.4.min.js" type="text/javascript"></script>
</body>
</html>
After implementation i change like this
<html>
<head>
<link rel="preload" href="http://fonts.googleapis.com/css?family=lato:400,100,200,300,500%7COpen+Sans:400,300,600,700,800%7COswald:300,400,700" as="style">
<link rel="preload" href="assets/js/jquery-1.12.4.min.js" as="script">
<link rel="stylesheet" href="http://fonts.googleapis.com/css?family=lato:400,100,200,300,500%7COpen+Sans:400,300,600,700,800%7COswald:300,400,700">
</head>
<body>
html contents
<script src="assets/js/jquery-1.12.4.min.js"></script>
</body>
</html>
But i can't notice any increase in speed . So please help to make this in correct way
i read the following article
https://developer.mozilla.org/en-US/docs/Web/HTML/Preloading_content .
But i can't figure out . Please help .
Or is there is any better method for page speed ?
Why this doesn't work
Preloading resources that are loaded directly in the HTML is useless. This is because the browser reads the preload at the same time as the actual resource reference.
Preloading is useful to reduce the length of your request waterfall.
Imagine the following situation:
style.css
body {
background-image: url(myimage.png);
}
index.html
<html>
<head>
<link rel="stylesheet" href="style.css" />
</head>
<body>
</body>
</html>
The process of loading the above page consists (roughly) of the following steps:
Download index.html
Parse the HTML file
Because of the link tag, download style.css
Parse the CSS file
Because of the background-image, download myimage.png
Parse the image and display it on the screen
This means your request waterfall is index.html -> style.css -> myimage.png.
By adding a preload for myimage.png the browser can download the image earlier, so your request waterfall becomes:
index.html +-> style.css
+-> myimage.png
Instead of 3, it is now only 2 requests long, which means faster load times.
What else can you do to improve (perceived) page load times?
Some common ways are:
Minify your assets (JavaScript, stylesheets)
Ensure your server has compression enabled for static assets
Only load resources actually required on page load first, then load other scripts later (like those for user interactions).
But to get a better overall view of the things you can improve you can use the Chrome Audit system (Lighthouse).
https://developers.google.com/web/updates/2016/03/link-rel-preload
See the above article link. I saw the link shared above. Preload never makes the page load the page fast. It only gives the priority to the files which is declared rel="preload" to load very early as the page loads up. You can read the article again Also the article shared by me. It will say the same.
You will need other methods to load the page fast. This method will not be helpful. There are few methods listed below you can use to make page load faster.
You can minify css and js files which will load very very fast than normal file.
You can minify script and css files from (https://www.minifier.org/) here.
Avoid external links of css and js files
Avoid spaces and Newlines in code.
Use compressed images which will also load faster.
Enable Caching.
As I have enabled the HTTP2 protocol of IIS, but the requests of the main javascript files were still queueing. According to the explanation of queueing by Chrome, I really don't know what cause this.
You can check at here: https://app.youjustgo.com/zh/
Queueing:
HTTP/2 means that more assets can be downloaded at once - not that they will be.
Browsers have various heuristics as to what to download and when.
For example, if an image is needed by a CSS file, then that image cannot be requested until the CSS file is downloaded and processed for example (ignoring preload). So in this case the CSS and the image will not download in parallel despite HTTP/2 allowing this.
Another issues is that <script> tags can change the content of the page, so unless it is explicitly marked as async (or defer) it is "render blocking". This means any JavaScript further down the page will not be run until the <script> tag is run. Now a browser could scan ahead and download the future scripts and just not run them until it needs to, if it wants, with the slight risk that it's a wasted download if the scripts subsequently are not actually needed. That's up to the browser and maybe Chrome decides it's not worth while to do this.
Looking at your specific site, your home page looks to be made up of basically only script tags. You could investigate the use of async or defer to allow more downloads to happen in parallel, but if you want the real performance improvement, you probably should go back to the basics of coding HTML, with CSS, and then enhancing it with JavaScript, rather than coding it all with JavaScript.
I'm also not sure of what the point of your preloading of your CSS is?
<link rel='preload' href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.37.0/mapbox-gl.css' as="style" onload="this.onload=null;this.rel='stylesheet'" />
<link rel='preload' href='https://api.mapbox.com/mapbox-gl-js/plugins/mapbox-gl-directions/v3.0.2/mapbox-gl-directions.css' as="style" onload="this.onload=null;this.rel='stylesheet'" />
<link rel="preload" href="https://npmcdn.com/angular2-toaster#2.0.0/toaster.css" as="style" onload="this.onload=null;this.rel='stylesheet'" />
<link rel="preload" href="//cdn.jsdelivr.net/jquery.slick/1.6.0/slick.css" as="style" onload="this.onload=null;this.rel='stylesheet'"/>
<link rel="preload" href="//cdn.jsdelivr.net/jquery.slick/1.6.0/slick-theme.css" as="style" onload="this.onload=null;this.rel='stylesheet'"/>
Preload is intended for assets that are not immediately apparent to the browser (like the image example above) to allow it to start downloading earlier. Here you are using it to preload CSS. The only advantage is it will not be render blocking and then you use the onload function to display it. However CSS normally is render blocking for a reason - otherwise your content looks unstyled. And because it is preloaded it's requested as high priority (which the CSS would have been requested as anyway), so not sure what advantage this is giving you to be honest. Very confused...
I'm pretty new to HTML&CSS, and I'm building my first website.
My head tag looks like this:
<head>
<meta charset="utf-8">
<meta name = "viewport" content = "width=device-width, minimum-scale=1, maximum-scale=1">
<meta name = "apple-mobile-web-app-capable" content = "yes" />
<link type="text/css" rel="stylesheet" href="css/normalize.css">
<link type="text/css" rel="stylesheet" href="http://fast.fonts.net/cssapi/739d414f-2430-436c-b2cf-5b84cc45995c.css">
<link type="text/css" rel="stylesheet" href="css/mobile.css">
<link type="text/css" rel="stylesheet" href="css/projects2.css">
<link type="text/css" rel="stylesheet" media="screen and (min-width:680px)" href="css/tablet.css">
<link type="text/css" rel="stylesheet" media="screen and (min-width:1400px)" href="css/desktop.css">
<title>Yulie Wollman | Projects </title>
</head>
I have 2 questions regarding to the CSS:
First, is multiple external CSS files influence my loading times? is it better to merge them into one big CSS file?
Secondly, will the media screen css link tags influence my loading times on smaller resolutions than 680px/1400px?
Thank you,
Boaz Keren Gil
With HTTP 1.0/1.1 every single HTTP request comes with overhead so the fewer requests the better.
You should work to keep the CSS segregated for your ease of coding at the server but combine them and then serve a single CSS compiled "file" to the client.
<?php
header('Content-Type: text/css; charset=UTF-8');
include('css/normalize.css');
include('css/mobile.css');
include('css/projects2.css');
?>
If you're running Apache you'll need to ensure you can execute PHP inside of the file type you use (e.g. .css)...
AddType application/x-httpd-php5 .css
...just make sure that you serve the correct mime FROM the file itself when you do this.
From my experience I would've said that one request is always better that lots of requests, so one big css is , in this case better, BUT if you have really big css file for lots of pages, and you'll load it on every page even if 99% of it's style are not necessary - that's not good at all. So decide it for your own case: few pages, small css - merge it to one, big project, lots of pages - separate requests on each.
And for second - nop,they will not.
Overall question Yes, it does influence load time. Each external css file is a additional request so it does add overhead.
However, the browser will cache the css so the next request will not suffer that much.
In general, if all pages in the site use the same css I would combine them and minimize them once deployed into your production environment
There are tools available like YSlow from Yahoo or Page Speed from Google that give you great insight in what is happening.
https://developer.yahoo.com/yslow/
https://developers.google.com/speed/pagespeed/?hl=nl
You can also use plugins for your browser to see the effect.
Generally it is recommended to reduce the number of http requests, especially for the websites targeting mobile browsers. The mobile networks have usually high latency (could be 300ms per request), then for 10 referenced files (css, javascript) it is 300 * 10 = 3 seconds loading time.
I started learning less css. Is there any possibility to import different less files
based on view port meta tag. I want to write my own less files for different resolutions.
I also want to know "How does the viewport meta tag works? "
I want to know from the meta tag
how the device width is set to "width" property of the meta tag and the corresponding media
query getting executed.
AFAIK you can't do this with viewport metatag. You can use media queries for this: https://developer.mozilla.org/en-US/docs/Web/Guide/CSS/Media_queries
When compiling Less client site (see: http://lesscss.org/#usage) you could do for example this:
<html>
<head>
<link rel="stylesheet" media="(max-width: 767px)" href="green.less" />
<link rel="stylesheet" media="(min-width: 768px)" href="red.less" />
<script src="less.js" type="text/javascript"></script>
</head>
<body>
<p>color this text</p>
</body>
</html>
with:
green.less: p{color:green;} and
red.less: p{color:red;} and
Also read http://andydavies.me/blog/2012/12/29/think-twice-before-using-matchmedia-to-conditionally-load-stylesheets/
In most cases you don't use client side compiling for production. Even preprocessors should be used only during the development process. In the production environment the real resulting CSS code should be used. When install LESS on the server, via npm, a compiler for server side compiling will be installed too.
Instead of using media queries to load different resources you could use them inside your less files. For the example above your less code should look like:
p{color:green;}
#media(min-width: 768px)
{
p{color:red;}
}
By adding media queries to <link> element it won't prevent the browser from downloading that css file.
The css file with the media query will be downloaded but it might not be a critical resource and it might not render blocking.
Finally, note that "render blocking" only refers to whether the browser has to hold the initial rendering of the page on that resource. In either case, the browser still downloads the CSS asset, albeit with a lower priority for non-blocking resources.
More details https://developers.google.com/web/fundamentals/performance/critical-rendering-path/render-blocking-css