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Definition and sourcesKNOWLEDGE / FROM A TO Z
Glossary
Technology, explained clearly. Find a term, choose a letter or narrow the topic. Definitions include sources and their review date.
Terms 28 / 685
Clear filtersHard bounce
A permanent delivery failure, such as a nonexistent address. The contact usually needs removal from active sending or correction.
Definition and sourcesHard disk drive
Storage using rotating magnetic platters. Mechanical access affects latency; capacity, reliability and performance depend on the specific model.
Definition and sourcesHashtag
A word or phrase preceded by # to label a topic. Search and distribution behaviour depends on the platform.
Definition and sourcesHeadless commerce
An architecture separating the storefront from commerce services through APIs. It offers presentation flexibility but adds integration, SEO and frontend-maintenance responsibilities.
Definition and sourcesHigh availability
Designing a service to limit disruption despite component failures. Redundancy needs tested failover and removal of single points of failure; it does not eliminate risk.
Definition and sourcesHosting
Providing resources needed to operate a website or application. Hosting involves more than storage: computing, networking and maintenance matter. Selection depends on project requirements and the provider's responsibilities.
Definition and sourcesHreflang
Markup identifying alternative language or regional versions. It should point to genuine equivalents with reciprocal consistency; it does not translate content automatically.
Definition and sources.htaccess
An Apache configuration file affecting a directory when the server permits overrides. It can control redirects and access. It is not universal to every hosting server; Nginx does not read it like Apache.
Definition and sourcesHTML (HyperText Markup Language)
A markup language describing the structure and meaning of web content, including headings and forms. HTML is not a general-purpose programming language. CSS and JavaScript commonly provide styling and interactivity.
Definition and sourcesHTML headings
The h1–h6 elements express content hierarchy, not font size. One principal h1 is a clear editorial convention. The number of h1 elements is not a simple Google ranking rule.
Definition and sourcesHTML title element
An imprecise colloquial name for HTML's title element, not a meta tag. It names the page; Google may generate a different result title.
Definition and sourcesHTTP (HyperText Transfer Protocol)
An application protocol using requests and responses, including for websites and APIs. It defines methods, headers and statuses. Protocol statelessness does not prevent applications from implementing sessions.
Definition and sourcesHTTP 301 (permanent redirect)
An HTTP status indicating a resource has moved permanently. The server normally provides the new address in Location. It is a redirect, not an error, and does not guarantee preserved search rankings.
Definition and sourcesHTTP 302 (temporary redirect)
An HTTP status indicating a temporary redirect while the original address remains the reference. It is not an error. Indexing effects depend on context rather than a blanket rule that 302 never affects search.
Definition and sourcesHTTP 401
An HTTP response indicating missing valid authentication. The server should provide a WWW-Authenticate challenge; it differs from a 403 permission refusal.
Definition and sourcesHTTP 403 (forbidden)
An HTTP status indicating that the server refuses the request, possibly because of permissions or access rules. A TLS certificate failure is not a 403 response. Resolve permissions with the administrator instead of bypassing protections.
Definition and sourcesHTTP 404 (not found)
An HTTP status indicating that a resource was not found or its existence is not disclosed. Check addresses and links. DNS failure happens at a different stage and is not itself an HTTP 404 response.
Definition and sourcesHTTP 408
An HTTP status for the server timing out while waiting for the client's request. It differs from 504, involving a gateway waiting for another server.
Definition and sourcesHTTP 500 (server error)
A general HTTP status signalling an unexpected server-side problem. It does not identify a specific cause. Diagnosis requires safe inspection of logs and configuration; updating PHP at random is not a universal fix.
Definition and sourcesHTTP 503
An HTTP status indicating temporary unavailability, such as overload or maintenance. Retry-After can suggest when the client should retry.
Definition and sourcesHTTP 505 (version not supported)
An HTTP status indicating that the server does not support, or refuses to support, the major protocol version used in the request. It concerns HTTP, not the browser version or a general network outage.
Definition and sourcesHTTP security headers
Headers controlling selected browser protections, such as CSP and HSTS. They need application-specific configuration; their presence does not prove absence of vulnerabilities.
Definition and sourcesHTTP Strict Transport Security
A browser policy enforcing HTTPS for a host. Long lifetimes and subdomain coverage should be enabled only after the full scope is ready.
Definition and sources