CS 511-Week 4:Topic 45-47

     

CS 511-Web Engineering

Week 4

Topic 45-47

CS 511-Week 4:Topic 45-47

Topic 45:

Fixed positioning:

Fixed positioning is a CSS property that is not commonly utilized, but it offers a specific way to position elements on a webpage. It functions similarly to absolute positioning, but with a significant distinction. Instead of being positioned relative to its closest positioned ancestor, a fixed position element is positioned relative to the viewport or the browser window.

When an element is assigned a fixed position, it remains in a fixed location on the screen, regardless of any scrolling actions performed by the user. As the user scrolls up or down the page, the fixed element stays fixed in its specified position.

The primary use of fixed positioning is to ensure certain elements remain visible and easily accessible to users at all times, particularly when navigating a website or when displaying advertisements. By assigning a fixed position to navigation menus, for example, they will persistently stay in view, even if the user scrolls through a lengthy webpage. This enhances the user experience by providing constant access to important navigation options, regardless of the user's position on the page.

Advertisements often employ fixed positioning as well. This allows them to remain visible on the screen, maintaining their intended prominence and ensuring they are always within the user's sight, irrespective of scrolling behavior.

To summarize, fixed positioning is a CSS property that allows elements to be positioned relative to the browser window rather than their containing elements. This feature is commonly used for navigation menus and advertisements to keep them in a fixed location on the screen, guaranteeing their visibility and accessibility as the user scrolls through a webpage.

Topic 46:

The use of the CSS float property allows elements to be moved from their normal position in the document flow, resulting in interesting layout effects. When an element is floated, it is positioned to the far left or far right of its containing block, and the remaining content "reflows" around it.

Floating within a container means that the floated item is moved to the left or right side of its containing block. This allows other content to wrap around the floated element, creating a visually appealing layout. For example, if an image is floated to the left within a text container, the text will flow around the image on the right side.

One common application of floats is to position multiple items side by side on the same line. By floating multiple elements, they can be arranged horizontally, creating a multi-column effect. When multiple items are floated in proximity, each floated item will be placed next to the previously floated item, and any remaining content will flow around all the floated elements.

To control the flow of elements around floated items, the clear property can be used. The clear property specifies whether an element should be positioned below any floated elements that come before it. By setting the clear property to "left," "right," or "both," an element can be prevented from being adjacent to a floated element on the specified side(s). Alternatively, setting the clear property to "none" allows the element to be adjacent to other elements, including floated ones.

However, issues can arise when a floated element is contained within a block that only contains floated content. In such cases, the containing block may appear to "disappear" because it collapses in height. This occurs because floated elements are taken out of the normal document flow, and the containing block no longer recognizes their height for layout purposes. To address this issue, techniques like using the clearfix method or applying overflow:hidden to the containing block can be employed to restore its proper dimensions and prevent content from overlapping or being obscured.

In summary, the CSS float property allows elements to be moved from their original position, enabling creative layout designs. Floating elements within a container positions them to the left or right, with the surrounding content flowing around them. Floats are commonly used to arrange multiple items side by side. The clear property can be used to control the positioning of elements in relation to floated items. However, when floated elements are contained within a block that solely consists of floated content, the containing block may collapse in height, requiring additional measures to restore its dimensions and prevent layout issues.

Topic 47:

Overlaying and Hiding Elements:

In CSS, there are common design tasks that involve overlaying elements on top of each other or selectively hiding and displaying elements. Achieving these tasks often requires the use of positioning techniques. Positioning allows elements to be precisely located within a container or relative to other elements on the page.

To overlay elements, positioning is crucial. Elements can be positioned using CSS properties like position: relative, position: absolute, or position: fixed. Relative positioning establishes a positioning context for subsequent absolute positioning, enabling elements to be moved relative to their normal position within a container. Absolute positioning allows elements to be placed at specific coordinates within a container, disregarding their original position in the document flow. Fixed positioning, on the other hand, positions elements relative to the viewport, making them stay in a fixed location even when the user scrolls.

When it comes to hiding elements, CSS provides two main approaches: using the display property and the visibility property.

The display property is used to control the visibility and layout behavior of elements. By setting display: none, an element is effectively removed from the document flow, as if it doesn't exist. The element is hidden, and the space it occupied is no longer allocated. This can be useful when you want to completely hide an element and adjust the layout accordingly. However, it's important to note that when an element is hidden using display: none, it will not be accessible or interactable by users, and any associated JavaScript events or styles will not apply.

The visibility property, on the other hand, allows you to selectively hide an element while still preserving its space in the layout. By setting visibility: hidden, the element becomes invisible, but its original space is maintained. This means that even though the element is not visible, it still affects the layout and may interact with other elements. For example, if an element is hidden with visibility: hidden, it will still occupy space, and other elements will not overlap with it. This property is commonly used when you want to hide an element but keep its layout impact intact.

In summary, CSS provides different positioning techniques to overlay elements or adjust their position relative to other elements. The display property is used to completely remove an element from the document flow, hiding it and freeing up the space it occupied. On the other hand, the visibility property allows you to hide an element while maintaining its space in the layout. Both techniques have their uses depending on the desired effect and layout requirements of a web page.

Assessment:

CS 511-Week 4:Topic 45-47

Which CSS property is used to position elements relative to the viewport or browser window? 

a) Fixed positioning 

b) Relative positioning 

c) Absolute positioning 

d) Float positioning
Answer: a) Fixed positioning

Which CSS property is commonly used to ensure navigation menus remain visible as the user scrolls? a) Display property 

b) Float property 

c) Visibility property 

d) Fixed positioning
Answer: d) Fixed positioning

What happens to a floated element within a container? 

a) It moves to the top of the container 

b) It moves to the bottom of the container 

c) It moves to the left or right side of the container 

d) It disappears from the container
Answer: c) It moves to the left or right side of the container

What happens when a floated element is contained within a block that only contains floated content? 

a) The floated element disappears 

b) The containing block collapses in height 

c) The floated element expands to fill the container 

d) The containing block becomes fixed in position
Answer: b) The containing block collapses in height

When an element is hidden using the display property, what happens to the space it occupied? 

a) The space is maintained 

b) The space is freed up 

c) The space is shifted to the right 

d) The space is shifted to the left
Answer: b) The space is freed up

Which CSS property is used to selectively hide an element while preserving its space in the layout? 

a) Position property 

b) Float property 

c) Visibility property 

d) Display property
Answer: c) Visibility property

What is the main difference between fixed positioning and absolute positioning? 

a) Fixed positioning is relative to the viewport, while absolute positioning is relative to the containing element. 

b) Fixed positioning allows elements to move, while absolute positioning keeps them fixed. 

c) Fixed positioning is commonly used for advertisements, while absolute positioning is used for navigation menus. 

d) Fixed positioning is more commonly used than absolute positioning.
Answer: a) Fixed positioning is relative to the viewport, while absolute positioning is relative to the containing element.

Which positioning property is commonly used to create interesting layout effects by moving elements from their normal position in the document flow? 

a) Fixed positioning 

b) Relative positioning 

c) Absolute positioning

 d) Float positioning
Answer: c) Absolute positioning

THE END 😊