378. [ Recursion ](/en-US/docs/Glossary/Recursion)
    379. [ Reflow ](/en-US/docs/Glossary/Reflow)
    380. [ Regular expression ](/en-US/docs/Glossary/Regular_expression)
    381. [ Render-blocking ](/en-US/docs/Glossary/Render_blocking)
    382. [ Rendering engine ](/en-US/docs/Glossary/Rendering_engine)
    383. [ Repaint ](/en-US/docs/Glossary/Repaint)
    384. [ Replay attack ](/en-US/docs/Glossary/Replay_attack)
    385. [ Repo ](/en-US/docs/Glossary/Repo)
    386. [ Reporting directive ](/en-US/docs/Glossary/Reporting_directive)
    387. [ Representation header ](/en-US/docs/Glossary/Representation_header)
    388. [ Request header ](/en-US/docs/Glossary/Request_header)
    389. [ Resource Timing ](/en-US/docs/Glossary/Resource_Timing)
    390. [ Response header ](/en-US/docs/Glossary/Response_header)
    391. [ Responsive web design ](/en-US/docs/Glossary/Responsive_web_design)
    392. [ REST ](/en-US/docs/Glossary/REST)
    393. [ RGB ](/en-US/docs/Glossary/RGB)
    394. [ RIL ](/en-US/docs/Glossary/RIL)
    395. [ Robots.txt ](/en-US/docs/Glossary/Robots.txt)
    396. [ Round Trip Time (RTT) ](/en-US/docs/Glossary/Round_Trip_Time)
    397. [ Routers ](/en-US/docs/Glossary/Routers)
    398. [ RSS ](/en-US/docs/Glossary/RSS)
    399. [ Rsync ](/en-US/docs/Glossary/Rsync)
    400. [ RTCP (RTP Control Protocol) ](/en-US/docs/Glossary/RTCP)
    401. [ RTF ](/en-US/docs/Glossary/RTF)
    402. [ RTL (Right to Left) ](/en-US/docs/Glossary/RTL)
    403. [ RTP (Real-time Transport Protocol) and SRTP (Secure RTP) ](/en-US/docs/Glossary/RTP)
    404. [ RTSP: Real-time streaming protocol ](/en-US/docs/Glossary/RTSP)
    405. [ Ruby ](/en-US/docs/Glossary/Ruby)
    406. [ Safe ](/en-US/docs/Glossary/Safe)
    407. [ Same-origin policy ](/en-US/docs/Glossary/Same-origin_policy)
    408. [ SCM ](/en-US/docs/Glossary/SCM)
    409. [ Scope ](/en-US/docs/Glossary/Scope)
    410. [ Screen reader ](/en-US/docs/Glossary/Screen_reader)
    411. [ Script-supporting element ](/en-US/docs/Glossary/Script-supporting_element)
    412. [ Scroll boundary ](/en-US/docs/Glossary/Scroll_boundary)
    413. [ Scroll chaining ](/en-US/docs/Glossary/Scroll_chaining)
    414. [ Scroll container ](/en-US/docs/Glossary/Scroll_container)
    415. [ SCTP ](/en-US/docs/Glossary/SCTP)
    416. [ SDK (Software Development Kit) ](/en-US/docs/Glossary/SDK)
    417. [ SDP ](/en-US/docs/Glossary/SDP)
    418. [ Search engine ](/en-US/docs/Glossary/Search_engine)
    419. [ Second-level Domain ](/en-US/docs/Glossary/Second-level_Domain)
    420. [ Secure Context ](/en-US/docs/Glossary/Secure_Context)
    421. [ Secure Sockets Layer (SSL) ](/en-US/docs/Glossary/SSL)
    422. [ Selector (CSS) ](/en-US/docs/Glossary/CSS_Selector)
    423. [ Self-Executing Anonymous Function ](/en-US/docs/Glossary/Self-Executing_Anonymous_Function)
    424. [ Semantics ](/en-US/docs/Glossary/Semantics)
    425. [ SEO ](/en-US/docs/Glossary/SEO)
    426. [ Serializable object ](/en-US/docs/Glossary/Serializable_object)
    427. [ Serialization ](/en-US/docs/Glossary/Serialization)
    428. [ Server ](/en-US/docs/Glossary/Server)
    429. [ Server Timing ](/en-US/docs/Glossary/Server_Timing)
    430. [ Session Hijacking ](/en-US/docs/Glossary/Session_Hijacking)
    431. [ SGML ](/en-US/docs/Glossary/SGML)
    432. [ Shadow tree ](/en-US/docs/Glossary/Shadow_tree)
    433. _[ Shallow copy ](/en-US/docs/Glossary/Shallow_copy) _
    434. [ Shim ](/en-US/docs/Glossary/Shim)
    435. [ Signature ](/en-US/docs/Glossary/Signature)
    436. [ SIMD ](/en-US/docs/Glossary/SIMD)
    437. [ Simple header ](/en-US/docs/Glossary/Simple_header)
    438. [ Simple response header ](/en-US/docs/Glossary/Simple_response_header)
    439. [ SISD ](/en-US/docs/Glossary/SISD)
    440. [ Site ](/en-US/docs/Glossary/Site)
    441. [ Site map ](/en-US/docs/Glossary/Site_map)
    442. [ SLD ](/en-US/docs/Glossary/SLD)
    443. [ Sloppy mode ](/en-US/docs/Glossary/Sloppy_mode)
    444. [ Slug ](/en-US/docs/Gloss