Add Aria recommandations changes

[Cqoicebordel]

Let's add a few changes to improve accessibility.

EDIT by @kvch:

Result from the accessibility test by the Accessibility Foundation for the Oscar theme:

• Non-text content
  • remove redundant alt texts from image results in info box
  • remove redundant alt texts from images in Videos, Social Media and Music
• Info and relationship
  • do not use h1 element for the logo
  • indicate visually active tab programmatically on the page Preferences
  • select and input tags are not connected programmatically on the page Preferences
  • use scope="col" for headers to describe properties in the Engines table
  • use scope="row" for headers for the name of the engines in the Engines table
• Use of colour
  • links should be distinguished from other text not only by colour (e.g. underline)
  • indicate too high max time by e.g. icon not only by colour
• Contrast
  • 4.5:1 contrast value for normal text
  • 4.5:1 contrast value for white texts on green buttons such as ‘Wikipedia (en)’
  • 4.5:1 contrast value for green URLs below each result
  • 4.5:1 contrast value for engine names (grey texts next to those links, such as ‘google scholar’)
  • 4.5:1 contrast value for focused tab on preferences and blue links
  • 4.5:1 contrast value for text on Save button
  • 4.5:1 contrast value for label "supported"
  • 4.5:1 contrast value for label "not supported"
  • 4.5:1 contrast value for grey text and slightly grey background on Answerers page
• Resize text
  • maximum-scale in meta tag have to be at least 2.0
• Non-text contrast
  • 3:1 contrast value for search input border
  • 3:1 contrast value for borders of the input fields for period and language in Advanced search
  • 3:1 contrast value for select on Preferences under General section
  • 3:1 contrast value for focused tab on Preferences
  • 3:1 contrast value for Allow engines for both on and off state
• Keyboard
  • make "Advanced settings" openable and usable with keyboard
  • switch between different tabs on Preferences with keyboard
  • toggle on-off buttons with keyboard for Engines and Plugins
• Bypass blocks
• Link purpose
  • add label to proxied and cached to show what those are
  • Files >> magnet link (add label)
  • Map >> show map, show details (add label)
  • Videos >> show video (add label)
• Language of page
  • when language of the UI is changed, change lang as well
• Error identification
  • provide more info about error when search query is empty
• Labels and instructions
  • add label/info to Time range search and Language
• Parsing
  • remove unnsecessary </small>
  • remove overflow:none as none is invalid
  • check page with W3C validator
• Name, role, value

[asciimoo]

Most of the issues are fixed, the remaining ones are only recommended and as I see the majority of other sites don't implement them, so I'm closing this issue. Feel free to reopen if you think anything else should be implemented from the above list.