www.shopyamatoya-jp.com

When JavaScript takes a long time to execute it can slow down website performance.

Duplicate JavaScript modules can slow down a website by requiring unnecessary downloads.

Inefficient animated content formats such as animated GIFs should be replaced by video.

This measures how long it takes a browser to render the first piece of content when someone visits a website.

This measures how long it takes a page to become fully interactive.

Lazily loading above the fold images can negatively affect performance.

When the main thread is busy the website may not respond quickly to user interactions.

Lazy-loading offscreen and hidden images after all critical resources have finished loading can significantly increase website performance.

The image used by the largest contentful paint element should be preloaded to maximize performance.

Avoid multiple page redirects as they introduce additional delays before the page can be loaded.

Delivering critical JavaScript and CSS inline and deferring all non-critical JavaScript and CSS can help prevent render blocking.

This measures the total amount of time that a page is blocked from responding to user input, such as mouse clicks, screen taps, or keyboard presses.

Minifying CSS files can reduce payload sizes.

Minifying JavaScript files can reduce payload sizes and script parse time.

Reduce unused rules from stylesheets to decrease bytes consumed by network activity.

Add preconnect resource hints to establish early connections to important third-party origins.

Text-based resources can be served with compression (gzip, deflate or brotli) to minimize network load.

Incorrect character encoding can result in garbled text and is properly declared in the charset attribute or the Content-Type HTTP response header.

Low-contrast text can be difficult or even impossible for many visitors to read.

Specifying a doctype prevents the browser from switching to quirks mode, which can cause a website to render in unexpected ways.

Users are mistrustful or confused by websites that request their location without context.

Images should be responsive and proportional to the display size and the pixel ratio to maximize image clarity.

Unload event listeners do not fire reliably and listening for them can intefere with website functionality and browser optimizations.

Users are mistrustful of or confused by sites that request to send notifications without context.

Correctly setting the viewport optimizes websites for mobile screen sizes and also prevents delays to user input.

Deprecated APIs are scheduled to be removed from browsers and can introduce errors and vulnerabilities.

Inspector issues indicate unresolved problems which can include security issues.

All websites should be protected with HTTPS including ones that don't handle sensitive data.

The value of an ARIA ID must be unique to prevent other instances from being overlooked by assistive technologies.

Properly ordered headings that do not skip levels convey the semantic structure of the page making it easier to navigate and understand when using assistive technologies.

If the website doesn't specify a language correctly screen readers might not be able to read the text correctly.

Specifying a valid land attribute helps screen readers announce text correctly.

Labels ensure that forms are announced properly by assistive technologies like screen readers.

Disabling zooming and scaling is problematic for users with low vision who rely on screen magnification to properly see the contents of a website.

A tabindex value greater than 0 implies an explicit navigation ordering which often creates frustrating experiences for users who rely on assistive technologies.

Screen readers have a specific way of announcing tables and when tables are not properly marked up, this creates the opportunity for confusing or inaccurate screen reader output.

Valid canonical links tell search engines which version of a page to crawl and display to users in search results.

Search engine users rely on the document title to determine if a page is relevant to their search.

Many sites provide different versions of a page based on a user's language or region and hreflang links tell search engines the URLs for all the versions of a page so that they can display the correct version.

Pages with unsuccessful HTTP status codes may not be indexed by search engines properly.

Search engines are unable to include websites in search results if they don't have permission to crawl them.

Descriptive link text helps search engines understand your content.

Meta descriptions may be included in search results to help convey website content.

Search engines can't index plugin content and many devices restrict plugins or don't support them.