When people tune out elements on a page that don't seem to be part of the site's core content, because it looks like an advertisement. 

Banner Blindness

When corporate content (such as announcements or promotions) looks too similar to advertisements, people will miss them due to "banner blindness." Intranets should have dedicated spaces for promotions so it is easier for users to tell the difference between ads and specific site content.

University of Michigan - Ann Arbor

Intranet tools and programs come and go, but bad UIs linger for years, impact employee productivity and morale, and ultimately increase organizational costs.

The Top Enduring Intranet-Design Mistakes: 7 Deadly Sins

https://www.nngroup.com/articles/top-intranet-design-mistakes/
Topics: Intranets,  Design Patterns
By Kara Pernice on November 27, 2016
Copyright © 1998-2021 Nielsen Norman Group, All Rights Reserved.

NNG Reference Article: The Top Enduring Intranet-Design Mistakes: 7 Deadly Sins

Most intranet search doesn't bring up the most relevant information. This can be for several reasons, some of which include 1) information on the internet is poorly tagged or categorized, and 2) information can be stored in areas the engine can't access.

Implications: People might act based on inaccurate information, or they end up wasting a lot of time struggling to find what they're looking for.

Poor Search Results

Content in a silo, is content that is difficult to discover because it is "walled-off" and hard to find. This can happen if the information is:
- not accessible via the search function
- absent from the global navigation and sub-navigation
- hidden based on user's role, due to personalization
- protected by a login wall

Implications: Silos make it more difficult for employees to find the right tools and updated content they need. Employees can feel alienated and disrespected if their level of access is different (lower) than that of other colleagues. Silos can waste the user's time, and lead to low job satisfaction.

Content in Silos

The visual layout of a page requires strategy, and it is impacted by
- text: color, size, typeface, bold/normal, line height/spacing
- graphics and images: position, size, color, relationship to content
- space: information density, white space, chunking
If text, graphics, or space are not used properly, pages can lack a clear visual hierarchy and appear cluttered. 

Implications: Poor visual layout can make scanning difficult, and make various elements less easy to distinguish. Users might find it difficult to determine which page elements are relevant to them. This can mean employees might miss important information, and/or waste their time.

Poor Visual Layout

There are plenty of cases of poor legibility of text throughout the intranet. This most often results from:
- poor contrast between text and page background
- tiny text
- flowery typefaces with complicated details

Implications: Text is difficult to read, and can be inconsistent across different devices. Glare from the sun can make low-contrast text unreadable. These mistakes force people to work harder to read what's on the page.

Illegible Text

Announcements & Promotions that Look like External Advertisements

Disappearing navigation is prevalent on the internet. This issue occurs because typically content strategy and information architecture are only partially planned ahead of time. Another reason this issue occurs is because of web designers' attempt follow the idea of progressive disclosure, and declutter the page as much as possible to create an immersive experience. 

Implications: Failing to consider "global navigation" an important and crucial part of the page, leads to poor navigational control and violates the "user control and freedom" UX design heuristic. It is unexpected and unsettling for users.

Global Navigation that Disappears

Too often, content is placed in an external link, and those links are presented on a page without much context. While this can save space by consolidating information, you should provide some information of value for the user regarding the link, before they follow it. It is considerate to help the user fill in the gaps of what they're missing before they click the link, so they can better determine whether they need to access the information from that link, or not. This gives the user more control and freedom to decide how to spend their time. 

Implication: The user either has to take extra time to follow the link in order to receive the missing content, or they don't have time to follow the link and end up never receiving said content. This can frustrate users.

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