Website Performance, Accessibility, SEO & Best Practices Guide

Creating a website that excels in performance, accessibility, and search engine optimization (SEO) is essential in today’s competitive online landscape. Whether you’re building a personal blog or an eCommerce platform, following best practices ensures a seamless user experience, boosts your site’s visibility, and helps you meet industry standards. In this guide, we’ll explore key rules and requirements for developing a website that stands out in terms of speed, accessibility, and optimization.

To create a high-performing, accessible, and SEO-optimized website that follows best practices, there are specific rules and requirements you should follow across different areas. These include web performance, accessibility standards, best practices for coding, and SEO techniques. Here’s a comprehensive guide:

1. Performance

Website performance is key for user experience and SEO ranking. A fast-loading website keeps users engaged and improves your chances of ranking well on search engines.

Key Rules for Best Performance:

1. Optimize Images: Compress and use modern image formats like WebP or AVIF, and set appropriate dimensions to prevent layout shifts.
2. Enable Browser Caching: Set up caching headers to store resources locally on users’ devices, reducing page load times on repeat visits.
3. Minimize HTTP Requests: Combine CSS, JavaScript, and image files when possible, and remove unnecessary assets.
4. Minify CSS, HTML, and JavaScript: Remove unnecessary characters like spaces, line breaks, and comments to reduce file sizes.
5. Lazy Load Content: Implement lazy loading for images, videos, and iframes so they only load when they are visible on the screen.
6. Use a Content Delivery Network (CDN): Distribute content across multiple servers to improve load times for users in different geographic locations.
7. Optimize Fonts: Use modern web fonts with font-display: swap for faster rendering and reduce font sizes using subsets.
8. Avoid Render-Blocking Resources: Defer or async loading of JavaScript and CSS files that are not critical to initial rendering.
9. Use Gzip or Brotli Compression: Compress text-based files (e.g., HTML, CSS, JS) to reduce file sizes sent to browsers.
10. Reduce Server Response Time: Improve your server’s performance by using a fast web host, optimizing databases, and minimizing server-side processing.

2. Accessibility (A11y)

Making your website accessible ensures that it can be used by people with disabilities. It also improves overall usability and is crucial for compliance with legal requirements like WCAG (Web Content Accessibility Guidelines).

Key Rules for Accessibility:

• Keyboard Navigation: Ensure all interactive elements (links, buttons, forms) can be navigated using the keyboard alone (use tab, shift-tab, and arrow keys).
• Alt Text for Images: Provide descriptive alt text for images, especially for informational and functional images, to help visually impaired users using screen readers.
• Semantic HTML: Use proper HTML5 tags (e.g., <header>, <main>, <article>, <nav>, <footer>) to give meaning to content, helping assistive technologies and search engines.
• Color Contrast: Ensure sufficient contrast between text and background to make content readable for users with visual impairments. Tools like WebAIM’s Contrast Checker can help.
• ARIA (Accessible Rich Internet Applications): Use ARIA attributes where necessary, such as aria-label for better screen reader support, but ensure you’re not overusing them.
• Resizable Text: Ensure that the website supports text resizing (up to 200%) without losing content or functionality.
• Form Accessibility: Ensure that form elements have associated labels, use fieldsets for grouped form elements, and add aria-required attributes where necessary.
• Focus Management: Ensure focus states are visible, and that focus order follows a logical sequence. Use skip to content links to help keyboard users navigate faster.
• Accessible Media: Provide transcripts for audio content, captions for videos, and ensure that media players support keyboard and screen readers.
• Error Identification and Suggestions: When users submit a form, clearly indicate any errors and provide suggestions for how to fix them.

3. Best Practices (Code & Security)

Adhering to coding best practices and security measures ensures your website is maintainable, secure, and scalable.

Key Rules for Best Practices:

• Use HTTPS: Secure your website using SSL certificates (HTTPS). Modern browsers flag non-secure websites, and Google prioritizes secure sites in search rankings.
• Avoid Inline Styles and Scripts: Use external stylesheets and JavaScript files to keep your code clean and more maintainable.
• Use Descriptive HTML Classes and IDs: Use semantic and self-explanatory class names and IDs (e.g., navbar instead of div1).
• Limit Dependencies: Minimize third-party libraries and plugins to avoid bloated code and potential security vulnerabilities.
• Error-Free JavaScript: Ensure JavaScript is free of errors by using linters like ESLint, and avoid global variables that can lead to conflicts.
• Optimize Database Queries: If your website is data-driven, use optimized queries to reduce load times and prevent bottlenecks.
• Content Security Policy (CSP): Implement CSP headers to prevent cross-site scripting (XSS) attacks by controlling which sources are allowed to execute scripts.
• Regularly Update Software: Keep your CMS, plugins, and libraries updated to patch security vulnerabilities and improve performance.
• Limit Password Visibility: Ensure login forms and authentication pages are secure, using hashed passwords and two-factor authentication (2FA).
• Use Service Workers: Leverage service workers to make your site work offline and improve load times through caching.

4. SEO (Search Engine Optimization)

Optimizing your site for search engines increases its visibility in organic search results, driving more traffic to your site.

Key Rules for SEO:

• Mobile-Friendly Design: Ensure your site is fully responsive, as Google prioritizes mobile-first indexing.
• Use Structured Data: Implement schema markup to help search engines better understand your content, which can improve how it is displayed in search results (e.g., rich snippets).
• Meta Tags: Include descriptive and unique meta titles and meta descriptions for each page. Keep meta titles under 60 characters and descriptions under 160.
• Header Tags (H1-H6): Use heading tags properly to structure content. Each page should have one <h1> tag that describes the main topic, with <h2> and <h3> for subtopics.
• Optimize URL Structure: Keep URLs short, descriptive, and include keywords. Avoid using numbers or random characters in URLs.
• Optimize Content for Keywords: Include relevant keywords in your page title, headers, and body text, but avoid keyword stuffing. Focus on user intent.
• Image Optimization for SEO: Use descriptive file names and alt text for images. Ensure images are compressed to improve load times.
• Internal Linking: Add internal links to relevant content on your site to improve navigation and help search engines crawl and index your pages.
• Sitemap and Robots.txt: Submit an XML sitemap to Google Search Console, and use a robots.txt file to manage which parts of your site search engines should or shouldn’t crawl.
• Page Speed: Ensure your site loads quickly, as Google uses page speed as a ranking factor. Use tools like Google PageSpeed Insights to monitor performance.
• Avoid Duplicate Content: Make sure each page has unique content. Duplicate content can confuse search engines and lead to lower rankings.
• Backlinks: Focus on getting high-quality backlinks from reputable sites. Google uses backlinks as a ranking signal to evaluate the authority of your content.
• Canonical Tags: Use canonical tags to indicate the preferred version of a page if there are multiple versions of the same content (e.g., when using query parameters).

Image Optimization

Image optimization is crucial for improving website performance, user experience, and SEO. Optimizing images involves reducing their file size without sacrificing too much quality, ensuring they load quickly and maintain a sharp appearance on all devices.

Here are key guidelines for optimizing images, including suggested sizes and dimensions:

1. File Formats

Choosing the right image format is the first step in optimization. Different formats serve different purposes:

• JPEG (JPG): Best for photographs or images with lots of colors and details. It supports compression, making it a good choice for balancing quality and size.
• PNG: Best for images with transparency or simple graphics like logos. However, it typically results in larger file sizes compared to JPEG.
• WebP: Modern format that offers superior compression for both photos and transparent images. Supported by most modern browsers, WebP can reduce file size while maintaining quality.
• SVG: Best for vector graphics such as icons and logos. Scalable without losing quality and typically smaller in file size.
• GIF: Use sparingly for simple animations, but for static images, WebP or PNG is often more efficient.

2. Image Compression

Compressing images reduces their file size and enhances loading speed. There are two types of compression:

• Lossy Compression: Reduces file size significantly by removing some data, which might slightly reduce quality (acceptable for most web usage). Use tools like TinyPNG, JPEG-Optimizer, or ShortPixel.
• Lossless Compression: Reduces file size without sacrificing any quality (ideal for graphics like logos). Tools like ImageOptim or PNGGauntlet can help.

Compression Guidelines:

• JPEG: Aim for a 70-80% quality setting. Use higher quality for high-res images and lower for thumbnails.
• PNG: Lossless compression (around 60-80% quality).
• WebP: Set quality between 70-80%, which usually offers better compression than JPEG without a noticeable quality drop.

3. Responsive Image Sizes

Implementing responsive images ensures that the right size of an image is loaded based on the user’s device and screen resolution.

General Size Recommendations for Web:

• Full-Width Background Images:
  • Desktop: 1920px wide
  • Tablet: 1280px wide
  • Mobile: 720px wide
• Content Images (inside articles or blogs):
  • Desktop: 1200px wide (with compression)
  • Tablet: 800px wide
  • Mobile: 400px wide
• Hero Images (large banners at the top of pages):
  • Desktop: 1600-1920px wide
  • Tablet: 1200px wide
  • Mobile: 720px wide
• Thumbnail Images:
  • Typically 150x150px (for galleries or post previews)
• Icons/Logos:
  • Use SVG where possible, but if raster, aim for 64x64px or 128x128px

Image Dimensions for High-DPI (Retina) Screens:

• Double the pixel dimensions for images displayed on high-DPI screens (e.g., 2x or 3x screens like Retina) to ensure sharpness. For example, if the required size is 400px, serve a 2x version at 800px for Retina devices.

4. Image Dimensions Based on Use Case

Different sections of a website have specific size and dimension recommendations:

• Homepage Slider or Banner:
  • Desktop: 1920x1080px or 1600x900px
  • Mobile: 750x1334px
• Gallery or Portfolio Images:
  • Aim for sizes between 1200px and 1600px wide, depending on the layout. Ensure aspect ratios are maintained.
• Featured Images for Blog Posts:
  • Desktop: 1200x630px (to accommodate social sharing dimensions like Open Graph)
  • Mobile: 750x375px
• Product Images (eCommerce):
  • Large view: 800x800px or 1000x1000px (for zoom functionality)
  • Thumbnails: 150x150px or 200x200px

5. Image Delivery

Use image delivery techniques to improve load times:

• Lazy Loading: Load images only when they are about to appear in the viewport, saving bandwidth and improving initial page load times. Use the loading="lazy" attribute for modern browsers.
• Content Delivery Network (CDN): Serve images from a CDN to reduce latency and improve performance by delivering images from servers closer to the user’s location.
• Image Srcset and Sizes Attribute: Use srcset to specify different image sizes for different screen widths. This allows the browser to choose the most appropriate image for the user’s device.

<img src="image-400.jpg" 
     srcset="image-400.jpg 400w, image-800.jpg 800w, image-1200.jpg 1200w"
     sizes="(max-width: 600px) 400px, (max-width: 1200px) 800px, 1200px" 
     alt="Sample Image">

6. Image Caching

Cache images to improve load times for returning visitors:

• Leverage Browser Caching: Set caching headers (Cache-Control or Expires) on your web server to store images on the user’s device for a certain period (e.g., 1 year).
• Use Image Versioning: Append a version number to image URLs (image-v2.jpg) to force browsers to download new versions when updates occur.

7. Alt Text for SEO and Accessibility

• Always include descriptive alt text for images, particularly for product photos and other important content. This not only helps visually impaired users but also improves SEO by helping search engines understand your images.

<img src="kitchen-renovation.jpg" alt="Modern kitchen renovation with marble countertops">

8. Avoid Large, Unnecessary Images

• Limit Large Background Images: For decorative background images, consider using CSS effects or SVG patterns instead of large image files.
• Use CSS or Icons for Simple Graphics: Instead of using images for simple icons or effects, use vector-based icons (e.g., FontAwesome, SVG) or CSS styles.

9. WebP Fallback

• Since not all browsers support WebP, use a fallback mechanism for unsupported browsers:

<picture>
  <source srcset="image.webp" type="image/webp">
  <img src="image.jpg" alt="Fallback image">
</picture>

10. Test and Monitor

Continuously test image performance using tools like:

• Google Lighthouse: Evaluates the performance, accessibility, best practices, and SEO of your website.
• Google PageSpeed Insights: Provides suggestions on image optimization.
• GTMetrix: Checks your page load performance and highlights oversized images.

Summary of Suggested Image Sizes and Dimensions: