Definitions beginning with P

404 page

Page shown for a missing resource, carrying HTTP status 404. Its text should explain the situation and offer a useful next step; displaying “not found” with status 200 is inconsistent.

Source consulted : MDN · 2026-10-17

In practice: keep the 404 status and offer a relevant path onward.

PaaS

Platform as a Service: managed cloud environment for building, deploying and operating applications without administering all infrastructure.

In practice: Check supported versions, backups and the option to move the application.

Page experience

Set of signals related to real page use, such as perceived speed, stability, interactivity, security and mobile display.

In practice: Test readability, stability and interaction on journeys that matter to visitors.

Page speed

A broad term for perceived and measured page speed. Separate content arrival, visual stability and response to actions, and record page, device and conditions instead of an unexplained single duration.

Reference: MDN : How browsers work · Source consulted 2026-10-18

In practice: Measure representative pages and networks with a goal tied to a real task.

PageRank

Historical Google algorithm evaluating, among other factors, the relative importance of pages from links connecting them.

In practice: Improve useful links between pages without trying to calculate an unavailable public value.

Paginated page

Part of a long list accessible at its own URL and linked to neighbouring parts.

In practice: open a later page directly and check neighbouring links.

Pagination

Organization of a list into successive portions, usually reached through URLs and links. It helps readers understand their position and limits the amount displayed at once. It differs from merely hiding items visually: later pages must remain reachable with understandable filters, ordering and position.

Reference: Google Search Central : Pagination · Source consulted 2026-10-18

In practice: open a later page directly, then use previous-page and browser-back controls. Check that selected criteria remain consistent and records do not repeat because of unstable ordering.

Paid search

Purchase of advertisements displayed in search engines according to queries, audiences or bids.

In practice: Compare click cost, enquiry quality and handling capacity before raising the budget.

Partitioned cookie

Cookie isolated by top-level site context rather than third-party state shared without that separation.

Reference: MDN : Set-Cookie

Test whether a component works under isolation without assuming a session shared across sites.

Passage ranking

Search engine ability to identify and value a particularly relevant passage within a longer page.

In practice: Structure sections so a precise answer makes sense with its context.

Passkey

Credential based on a cryptographic key pair bound to the service. It may be synchronised across devices or remain device-bound.

Reference: FIDO Alliance · Passkeys · Source consulted 2026-10-31

Source consulted : W3C · 2026-10-17

In practice: test enrollment, use across devices and account recovery.

Payload

Useful data carried by a message, depending on protocol and context. In HTTP exchanges, the term often refers to request or response body content, distinct from header metadata. Receiving it establishes neither conformity with the data contract nor permission to perform the requested action.

Reference: MDN : HTTP messages · Source consulted 2026-10-18

In practice: prepare fictional examples with expected fields, missing values and an incorrect type. Check each response and size limits; valid JSON syntax is insufficient to accept a business request.

Performance budget

Chosen limits for page costs, such as script bytes or rendering time. Give each limit a measurement method and decide what happens when it is exceeded.

Reference: web.dev : Performance budgets · Source consulted 2026-10-18

In practice: Set a limit per page type and review the weight added by each new component.

Permalink

Address intended to identify content over time, even when its presentation or technical storage changes. Stability depends on site management: “permanent” does not prevent deletion or broken links. When content moves, an equivalent destination or explicit removal status preserves an understandable route.

Reference: W3C : Cool URIs don’t change · Source consulted 2026-10-18

In practice: open an address retained in an old email after changing the site. Check the resulting content and any redirects; avoid addresses tied to a staff member or temporary internal organization.

Persona

Synthetic profile representing a user or customer type to guide content, services and journeys.

In practice: Ground each assumption in interviews or observations and record what remains uncertain.

Phishing

Deception impersonating a trusted person or service to obtain sensitive information. It may use messages, fake websites or calls.

Reference: NIST CSRC · Phishing · Source consulted 2026-10-31

Source consulted : MDN · Phishing · 2026-10-31

PHP

Server-side programming language widely used to produce dynamic Web pages and power CMS platforms such as WordPress.

In practice: Check the version running in production and extensions used by the project.

Pixel

Specify which pixel you mean: an image pixel, physical display pixel or CSS pixel. A CSS pixel need not correspond to one hardware pixel, particularly on high-density displays.

Reference: MDN : CSS pixel · Source consulted 2026-10-18

In practice: Distinguish CSS dimensions, screen density and file dimensions before exporting an image.

Plugin

Extension added to software to provide further capabilities, such as a form in a CMS. Its effect depends on configuration, dependencies and compatibility with the rest of the site. Installation still requires planning for updates, security, retained data and maintenance costs.

Reference: WordPress : Manage plugins · Source consulted 2026-10-18

In practice: establish how an extension is used before removing it. Test its replacement on a protected copy, then check associated forms, content and data; an inactive extension may still retain useful settings.

PNG

Lossless raster image format supporting transparency, suited notably to interfaces and crisp illustrations. Lossless compression preserves pixels, but photographs can produce large files. Compare formats according to the content and intended use.

Reference: MDN · Image file types and formats · Source consulted 2026-10-25

In practice: Keep this format when transparency or exact detail requires it and compare its size with alternatives.

Portrait permission

Documented agreement stating where and how a recognisable photograph of a person may be used.

In practice: retain the agreement scope with the file and pages where the photograph appears.

PostgreSQL

Open-source relational database management system known for rich capabilities and robustness.

In practice: Test restore, migrations and indexes on a representative data copy.

PPC

Pay per click: advertising model in which the advertiser pays when a user clicks the advertisement.

In practice: Set a spending limit and a measured objective beyond the click itself.

Preferred image

Representative image indicated through signals such as og:image or primaryImageOfPage to help platforms select a relevant preview.

In practice: Choose an accessible representative image consistent with the page rather than a decorative visual.

Preflight request

OPTIONS request sent by the browser before certain cross-origin exchanges to check advertised permissions. Its success does not guarantee acceptance of the subsequent business request.

Reference: MDN : Preflight request

Source consulted : MDN · 2026-10-17

Inspect the preliminary and actual requests; a correct first response does not prove the second succeeded.

Prelaunch checklist

List of checks before a website opens: journeys, content, forms, images, accessibility, indexing and redirects.

In practice: Have owners accept critical journeys and record known accepted defects before release.

Preview cache

Temporary copy of sharing metadata retained by a platform and sometimes displayed after an update.

In practice: allow the platform time to refresh an older preview.

Price effective date

Date from which a published price or term applies, helping distinguish the current offer from an older document or campaign.

In practice: record the effective date and check copies in cards, FAQs and translations.

PrimaryImageOfPage

Schema.org property linking a page to the main image representing it in structured data.

In practice: Point to the image that genuinely represents the page and remains available at a stable URL.

Product availability

Current state of a product or variant indicating whether it can be ordered and under which conditions.

In practice: update the page and product data when stock runs out.

Product difference

Difference between items whose practical effect on a choice is explained rather than merely listed.

In practice: explain when the difference matters in real use.

Product page

Page dedicated to a specific item, its characteristics, images, variants and decision-relevant terms.

In practice: check that someone can compare the item without contacting the seller.

Product variant

Identifiable product version differing by a property such as size, material or colour.

In practice: clearly show the chosen variant’s photo and terms.

Professional portrait

Photograph used to identify a person’s role in an organisation, with an agreed crop and use.

In practice: check the date, mobile crop and approved use of each portrait.

Progressive enhancement

Approach providing essential content and functionality first, then adding capabilities according to browser support. For example, a linked list remains usable when its JavaScript filter fails. Define and test that baseline rather than assuming failures will be rare.

Reference: MDN : Progressive enhancement · Source consulted 2026-10-18

In practice: Make the core action possible in base HTML, then add interactive convenience.

Progressive Web App

Web application using browser capabilities for an experience that can include installation and offline use. These capabilities depend on the browser and design. Installing the app does not automatically make its catalogue, sign-in or checkout available without a network.

Reference: MDN : Progressive web apps · Source consulted 2026-10-18

In practice: Test installation, updates, offline use and reconnection on target devices.

Prompt

Instruction, context or set of examples given to an AI model to guide its response or action.

In practice: Specify goal, context and output form, then retain test cases to detect regressions.

Prompt engineering

Design, testing and structuring of instructions intended to obtain more reliable and suitable AI model outputs.

In practice: Keep expected examples and failure cases to check every instruction change.

Prompt injection

Manipulation of an AI system through untrusted instructions, supplied directly or encountered in external content. They may conflict with the system’s intended rules.

Reference: OWASP GenAI · LLM01:2025 Prompt Injection · Source consulted 2026-10-31

In practice: Treat retrieved content as untrusted data and test attempts to change instructions.

Proxy

Intermediary relaying communication between a client and destination. Depending on placement and configuration, it can filter, forward or cache exchanges. It adds a step to examine in diagnosis; its presence does not automatically mean encryption or anonymity.

Reference: MDN : Proxy servers and tunneling · Source consulted 2026-10-18

In practice: Identify what it changes in requests and responses before blaming the origin server.

Push notification

Message sent by an application or website to a device after user permission.

In practice: Ask permission at a useful moment and allow alerts to be adjusted or stopped.

Python

General-purpose programming language widely used for the Web, automation, data and artificial intelligence.

In practice: Make dependencies and version explicit to reproduce processing on another machine.