Usabilty testing is performed for the purpose of making sure that a site meets the intended audiences needs, and that it is functional. According to hostinger.com a frustrating user experience on an eCommerce website will all but assure that an online shopper will not return. To make sure this doesn't happen, owners of websites have to make sure that the viewers of the site are satisfied with the overall appearance and navigation of the site. That is where usability testing comes in. There are many methods for usabilty testing from moderated in house testing where qualified researchers are hired to test the site, and are monitored to see how well they do navigating, to card sorting testing where different types of web content are offered in card form and testers are asked to reorder and organize the cards. They are then asked why they sorted in the manner that they did. This form of testing lets the owner know how hte users see the structure of the website, and it helps them to organize the site in a way that will be easily logically navigated.
According to usabilitygeek.com there are 3 main categories of usability testing.
Explorative: Explorative testing is used early in the development process to assess a preliminary design for usability
Assessment: Assesment testing is used midway through development. It evaluates real-time testing of technology to determine usability.
Comparative: Comparative testing as the name infers compares two or more designs against each other to distingush the strengths and weaknesses of each of them.
To answer the question about how different versions of browsers are tested, I had to find a third website. Software Testing Help.
To perform cross browser testing all you have to do is open your site in multiple browsers. Different browsers render sites differently. The colors, fonts, and other visual items my
or may not render how you intended on different browsers. Of course functionality is also something to consider in cross browser testing also. Cross browser testing can of course be done manually by simply opening your
site in different browsers and noting how they're rendered. However if you have a very large complicated site to evaluate their are multiple automated testing tools available. I'll list the first four that I found
below. Please note I have not tested these services and by listing them I am not endorsing them. These tools provide screenshots for subitted pages and links of how they look in different browsers. The show the rendition of the
pages at different resolutions accross multiple browsers. If a problem is encountered it is documented and screenshots are provided for further analysis. The generally support both web and mobile apps also.