5709a7858d5c197721be66d5218a79124abadb70
lrnassar
  Tue Mar 17 08:46:31 2026 -0700
Adding alt text to images across static documentation pages, CGI headers, markdown docs, and Pandoc templates. Content images receive AI-generated descriptive alt text; decorative images (icons, spacers, toggles) receive alt="" per WCAG best practice. Also adds Image Descriptions section to the accessibility page, and fixes Pandoc Lua writers to output alt attributes. 67 files, covering help docs, news archive, ENCODE pages, portal pages, and session examples. refs #37254

diff --git docs/hubs/hubBasics.md docs/hubs/hubBasics.md
index 87964bcc805..3770328b230 100644
--- docs/hubs/hubBasics.md
+++ docs/hubs/hubBasics.md
@@ -94,60 +94,60 @@
 shortLabel bigBed Required Settings
 longLabel A bigBed Example with Required Settings
 visibility pack
 type bigBed 12 +
 bigDataUrl gtexCaviar.chr7_155799529-155812871.bb
 ```
 
 The `type` line consists of three parts:
 
 - "bigBed" is the basic track type.
 - "12" indicates how many standard BED fields are included in your file. You may need to change this to match the number of standard BED fields in your file.
 - "+" tells the genome browser there are extra fields beyond the standard fields. If your file has no extra fields, replace this with a "." (e.g. type bigBed 12 .).
 
 Here is a screenshot of what this basic bigBed track looks like displayed in the Genome Browser:
 
-![](/images/bigBedReqSettings.png)
+![Browser display of a basic bigBed track configured with required settings only](/images/bigBedReqSettings.png)
 
 The bigBed format also offers a wide range of customization options for the display, from decorators to highlights. 
 Additionally, it offers extensive [filter controls](/goldenPath/help/hubQuickStartFilter.html), 
 [searching options](/goldenPath/help/hubQuickStartSearch.html), and mouseover configurations. 
 Our [trackDb documentation](/goldenPath/help/trackDb/trackDbHub.html) contains a full listing of settings available for the format.
 
 Here is the bigBed configuration with some commonly used settings, including filtering and mouseover configuration:
 
 ```
 track bigBedCommonSettings
 shortLabel bigBed Common Settings
 longLabel A bigBed Example with Commonly Used Settings
 visibility pack
 type bigBed 12 +
 bigDataUrl gtexCaviar.chr7_155799529-155812871.bb
 filterLabel.cpp CPP (Causal Posterior Probability)
 filter.cpp 0
 filterLabel.geneName Gene Symbol
 filterText.geneName *
 mouseOver $name; CPP: $cpp
 ```
 
 And here is what that track looks like in the Genome Browser:
 
-![](/images/bigBedCommonSettings.png)
+![Browser display of a bigBed track configured with commonly used optional settings](/images/bigBedCommonSettings.png)
 
 These common settings added options to the track configuration pop-up:
 
-![](/images/bigBedCommonSettingsPopUp.png)
+![Track configuration pop-up showing filtering and mouseover options for a bigBed track](/images/bigBedCommonSettingsPopUp.png)
 
 ## bigWig Tracks
 
 You can use [bigWig](/goldenPath/help/bigWig.html) tracks to display continuous annotations, 
 such as RNA-seq expression, conservation scores, or other genome signal scores. You can build a bigWig 
 using one of two plain-text formats: [wiggle](/goldenPath/help/wiggle.html) or [bedGraph](/goldenPath/help/bedgraph.html).
 
 ### Building a bigWig
 
 1. Download the `wigToBigWig` utility for your system type from our [download server](https://hgdownload.gi.ucsc.edu/downloads.html#utilities_downloads).
 
 2. Use this utility to build your bigWig:
    ```
    wigToBigWig in.bedGraph chrom.sizes myBigWig.bw
    ```
@@ -173,31 +173,31 @@
 shortLabel bigWig Example
 longLabel A bigWig Example with Commonly Used Settings
 visibility pack
 type bigWig -20 10.003
 bigDataUrl hg38.phyloP100way.chr7_155799529-155812871.bw
 color 60,60,140
 ```
 
 The `type` line consists of two parts:
 
 - "bigWig" is the basic track type
 - "-20 10.003" indicates the minimum and maximum of the data in the bigWig
 
 Here is what this looks like visualized in the Genome Browser:
 
-![](/images/bigWigReqSettings.png)
+![Browser display of a basic bigWig signal track with required settings only](/images/bigWigReqSettings.png)
 
 ## Grouping tracks
 
 Next, we'll provide a basic overview of how to group your tracks using composite tracks and super tracks. 
 This will allow you to pull similar data together under a single container.
 
 ### Composite Tracks
 
 Composite tracks can hold multiple tracks of the same type. For example, you use a composite to 
 group together a set of RNA-seq experiments, including replicates.
 
 Here's what the configuration might look like for a composite containing two bigWig tracks. There are two key 
 components of a composite: (1) the line "compositeTrack on" in the parent track stanza, and (2) including 
 "parent compositeName" for each track that will be part of the composite.
 
@@ -220,31 +220,31 @@
     visibility dense
 
     track compositeBigWig2
     bigDataUrl c.chr7_155799529-155812871.bw
     shortLabel bigWig #2
     longLabel bigWig in Composite Track Example #2
     parent compositeExample
     type bigWig 0 1
     color 0,255,0
     autoScale group
     visibility dense
 ```
 
 This composite track configuration will display like so:
 
-![](/images/compositeBigWig.png)
+![Composite track displaying multiple bigWig subtracks grouped together in the browser](/images/compositeBigWig.png)
 
 ### Super Tracks
 
 Super tracks are a more general type of container. They can contain tracks of different types and even composites.
 
 Configuring a basic super track is quite similar to composite tracks. There are two key components of a composite: 
 (1) the line "superTrack on" in the parent track stanza, and (2) including "parent superTrackName" for each track 
 that will be part of the super track.
 
 ```
 track superTrackExample
 shortLabel Super Track Example
 longLabel A super-track of related data of various types together: individual, multiWig, and composite
 superTrack on show
 html examplePage
@@ -272,31 +272,31 @@
         shortLabel ST bigWig composite #1
         longLabel A composite-contained bigWig in a super track example #1
         parent superTrackCompositeBigWig on
         type bigWig 0 1
         
         track superTrackCompositeBigWig2
         bigDataUrl c.chr7_155799529-155812871.bw
         shortLabel ST bigWig composite #2
         longLabel A composite-contained bigWig in a super track example #2
         parent superTrackCompositeBigWig on
         type bigWig 0 1
 ```
 
 Loading the example hub with this super track configuration looks like this:
 
-![](/images/superTrackEx.png)
+![Super track grouping bigBed, composite bigWig, and multiWig tracks in a folder hierarchy](/images/superTrackEx.png)
 
 ## Creating description pages
 
 If you plan to share your track hub more widely, you will want to create a description page for your tracks. A description 
 page could contain a short description of what the data represents, how the data was generated, a link to the associated paper, 
 or a contact email for questions regarding the data. Multiple tracks can use the same description page.
 
 We provide an [example description html](/goldenPath/help/examples/hubExamples/templatePage.html) that you can modify with the 
 details for your track. Once you've modified this example html for your track, add an `html` to the corresponding track stanza:
 
 ```
 track bigWigExample
 shortLabel bigWig Example
 longLabel A bigWig Example with Commonly Used Settings
 type bigWig -20 10.003