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A3 · Search Engine Optimisation (SEO)
Spec reference: Learning Aim A - Principles of Website Development Key idea: SEO helps websites rank higher in search results, bringing in more visitors organically.
SEO explained in 5 minutes
Organic vs Paid search results
When you search on Google, the results page (SERP) shows two types of results:
| Type | Description | Cost |
|---|---|---|
| Organic results | Pages ranked by Google's algorithm based on relevance and quality | Free |
| Paid results | Adverts that businesses have paid to appear at the top | Per click (PPC) |
Paid results are labelled "Sponsored" and appear at the very top. Organic results appear below. Most users trust organic results more - and most clicks go to organic results.
Why SEO matters: 75% of users never scroll past the first page of results. If your site isn't on page 1, it effectively doesn't exist for most users.
How search engines work
Search engines like Google use three processes:
- Crawling - automated bots (called "spiders" or "crawlers") visit web pages and follow links to discover content
- Indexing - the content is stored and organised in the search engine's database (the index)
- Ranking - when a user searches, the algorithm scores and orders all relevant indexed pages
The ranking algorithm considers hundreds of factors. Google's exact formula is secret, but the key factors are well understood.
Google's key ranking factors
| Factor | Explanation |
|---|---|
| Content quality | Well-written, original, relevant content ranks higher than thin or copied content |
| Backlinks | Links from other reputable websites to your site signal authority and trust |
| Mobile responsiveness | Google uses "mobile-first indexing" - your mobile version is ranked, not desktop |
| Page speed | Slow sites are penalised - Google measures loading time |
| HTTPS / Security | Sites with SSL certificates (https://) are preferred over http:// |
| Keywords | Your content should naturally include terms users search for |
| User experience (UX) | Bounce rate, time on page and click-through rate all signal quality |
| Crawlability | Google must be able to find and read your pages |
Long-term strategy
SEO results take months to appear. It is a long-term investment, not a quick fix. Unlike paid ads which stop working when you stop paying, good SEO continues to deliver traffic over time.
Meta tags
Meta tags are HTML tags placed in the <head> section of a web page. They provide information about the page to search engines and social media platforms - users don't see them on the page itself, but they have a significant impact on SEO and how the page appears in search results.
Core meta tags
html
<!-- Page title - shown in browser tab and as the blue clickable link in Google -->
<title>Sweet Delights Bakery | Artisan Cakes and Breads in Leicester</title>
<!-- Description - shown as the grey text below the link in Google search results -->
<meta name="description" content="Sweet Delights is Leicester's favourite artisan bakery.
Order fresh cakes, breads and cookies online. Locally sourced ingredients.">
<!-- Viewport - essential for mobile responsiveness -->
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- Robots - tell search engines whether to index this page -->
<meta name="robots" content="index, follow">
<!-- Character encoding -->
<meta charset="UTF-8">Open Graph tags (social sharing)
These control how the page appears when shared on Facebook, LinkedIn, etc.:
html
<!-- Title shown when shared on social media -->
<meta property="og:title" content="Sweet Delights Bakery">
<!-- Description shown when shared -->
<meta property="og:description" content="Leicester's favourite artisan bakery.">
<!-- Image shown as a preview card when shared -->
<meta property="og:image" content="https://sweetdelights.co.uk/images/banner.jpg">
<!-- The URL of the page -->
<meta property="og:url" content="https://sweetdelights.co.uk">
<!-- Type of content -->
<meta property="og:type" content="website">Twitter Card tags
Control how the page appears when shared on X (Twitter):
html
<meta property="twitter:card" content="summary_large_image">
<meta property="twitter:title" content="Sweet Delights Bakery">
<meta property="twitter:description" content="Leicester's favourite artisan bakery.">
<meta property="twitter:image" content="https://sweetdelights.co.uk/images/banner.jpg">
<meta property="twitter:site" content="@SweetDelights">What Google will NOT reward (black-hat SEO)
Avoid these practices - Google penalises them:
| Bad practice | Why it's penalised |
|---|---|
| Keyword stuffing | Cramming keywords unnaturally into content - looks spammy |
| Buying backlinks | Paid links are against Google's guidelines |
| Pop-ups that cover content | Poor user experience - Google penalises intrusive interstitials |
| Duplicate content | Copying content from other sites - no original value |
| Hidden text | White text on white background - manipulating crawlers |
Measuring SEO performance
Tools used to measure website performance and SEO:
| Tool | What it measures |
|---|---|
| Google Lighthouse | Performance, accessibility, SEO score (run from Chrome DevTools - F12) |
| Google Search Console | Which search queries bring users to your site, crawl errors |
| Google Analytics | Visitor numbers, bounce rate, time on page |
| W3C Validator (validator.w3.org) | Checks HTML and CSS are valid - errors can hurt crawling |
Lighthouse scores
Google Lighthouse gives your site a score out of 100 for: Performance, Accessibility, Best Practices, and SEO. Aim for 90+ in each category.
Summary
| Term | Meaning |
|---|---|
| SEO | Improving a website to rank higher in organic search results |
| Organic results | Unpaid search results ranked by Google's algorithm |
| Paid results | Adverts businesses pay to appear at the top of search results |
| Crawling | Search engine bots visiting and reading web pages |
| Indexing | Storing crawled content in the search engine's database |
| Meta tags | HTML tags in <head> that describe a page to search engines |
| Backlink | A link from another website to your site - signals authority |
| SERP | Search Engine Results Page |
Test Yourself
Question 1 of 5
What does SEO stand for?