Multimedia and Web Technology
Domain scope
This domain tests multimedia elements, file formats and compression, web page structure, CSS, HTTP and accessibility. Expect calculations of file size, format selection and identification of HTML or CSS errors.
Core rules
- Multimedia elements include text, graphics, audio, video and animation. Bitmap graphics store pixels; vector graphics store mathematical objects and scale cleanly.
- Lossless compression (PNG, GIF, FLAC) preserves exact data; lossy compression (JPEG, MP3, MP4) discards perceptual detail. JPEG suits photographs; PNG or GIF suits logos, screenshots and transparency.
- Uncompressed bitmap size = width × height × colour depth ÷ 8 bytes, before metadata.
- HTML provides structure; CSS controls presentation. Use alt text for informative images and label form controls.
Worked example
An 800 × 600 image uses 24-bit colour. Calculate its uncompressed size. Reasoning: pixels = 800 × 600 = 480,000. Bits = 480,000 × 24 = 11,520,000 bits. Bytes = 11,520,000 ÷ 8 = 1,440,000 bytes. In MiB: 1,440,000 ÷ 1,048,576 ≈ 1.37 MiB, or about 1.44 MB decimal. Compression reduces this; JPEG may be much smaller but introduces artefacts.
Traps
- Forgetting to divide bits by 8.
- Choosing JPEG for a sharp logo with text; artefacts appear.
- Using obsolete HTML tags such as font and claiming they are current best practice; CSS is preferred.
- Omitting alt text or using image as alt text, which fails accessibility.