1. Bad Search

Overly literal search engines reduce usability in that they're unable to handle typos, plurals, hyphens, and other variants of the query terms. Such search engines are difficult for new users and hurt everybody.

A related problem is when search engines prioritize results purely on the basis of how many query terms they contain, rather than on each document's importance.

Search is the user's lifeline when navigation fails. Even though advanced search can sometimes help, and search should be presented as a simple box, since that's what users are looking for.

2. PDF Files for Online Reading

Users hate coming across a PDF file while browsing, it breaks the flow of the user. Even simple things like printing or saving documents are difficult because standard browser commands don't work. Layouts are often optimized for a sheet of paper, which rarely matches the size of the user's browser window. Bye-bye smooth scrolling.

It is Worst, PDF is an undifferentiated blob of content that's hard to navigate.

PDF is great for printing and for distributing manuals and other big documents that need to be printed. Reserve it for this purpose and convert any information that needs to be browsed or read on the web pages.

3. Not Changing the Color of Visited Links

A good grasp of past navigation helps you understand your current location, since it's the culmination of your journey. Links are a key factor in this navigation process. Users can exclude links that proved futile in their earlier visits. Conversely, they might revisit links they found helpful in the past.

Most important, knowing which pages they've already visited frees users from unintentionally revisiting the same pages again and again.

These benefits only accrue under one important assumption: that users can tell the difference between visited and unvisited links because the site shows them in different colors. When visited links don't change color, users exhibit more navigational disorientation in usability repeatedly.

4. Non-Scannable Text

A wall of text is deadly for an interactive experience.

To draw users into the text and support scannability, use well-documented tricks:

• Subheads
• Bulleted lists
• Highlighted keywords
• Short paragraphs
• The inverted pyramid
• A simple writing style, and

CSS style sheets unfortunately give websites the power to disable a Web browser's "change font size" button and specify a fixed font size. About 95% of the time, this fixed size is tiny , reducing readability significantly for older people

Specify font sizes in relative terms -- not as an absolute number of pixels.

5. Not Answering Users' Questions

Users are highly goal-driven on the Web. They visit sites because there's something they want to accomplish -- maybe even buy your product. The ultimate failure of a website is to fail to provide the information users are looking for.

Sometimes the answer is simply not there and you lose the sale because users have to assume that your product or service doesn't meet their needs if you don't tell them the specifics Users don't have time to read everything, such hidden info might almost as well not be there.

The worst example of not answering users' questions is to avoid listing the price of products and services. ecommerce site would make this mistake Price is the most specific piece of info customers use to understand the nature of an offering, and not providing it makes people feel lost and reduces their understanding of a product line.

Knowing the price is key in both situations; it lets users differentiate among products and click through to the most relevant ones.