Added a sentence about VISTA enchancers

lessons/06_peak_visualization_with_igv.md

@@ -192,7 +192,7 @@ After loading the cKO IP replicate 3 BigWig track, your IGV session should look
 
 #### Loading tracks from URL
 
-Alternatively to loading a track from a local file, we can also load tracks from a URL. In this case, we will load [VISTA enchancers](https://enhancer.lbl.gov/vista/) that are availible for the Mouse genome on the [UCSC Genome Browser](https://genome.ucsc.edu/). The file uses bigBed format, which is used with hosted genome browsers liike the UCSC browser which allows the browser only load the relevant sections of genomes at a time and is less computaitonally intensive on a public genome browser. More information on bigBed can be found on the [UCSC page about bigBed](https://genome.ucsc.edu/goldenpath/help/bigBed.html). In order to load  a file from a URL, left-click on <kbd>File</kbd> in the top-left and select <kbd>Load from File...</kbd>. Next, enter this URL into the URL blank:
+Alternatively to loading a track from a local file, we can also load tracks from a URL. In this case, we will load [VISTA enchancers](https://enhancer.lbl.gov/vista/) that are availible for the Mouse genome on the [UCSC Genome Browser](https://genome.ucsc.edu/). The VISTA enhancers are curated set of computaitnally predicted and *in vivo* validated enhancer elements in mouse. The file uses bigBed format, which is used with hosted genome browsers liike the UCSC browser which allows the browser only load the relevant sections of genomes at a time and is less computaitonally intensive on a public genome browser. More information on bigBed can be found on the [UCSC page about bigBed](https://genome.ucsc.edu/goldenpath/help/bigBed.html). In order to load  a file from a URL, left-click on <kbd>File</kbd> in the top-left and select <kbd>Load from File...</kbd>. Next, enter this URL into the URL blank:
 
 ```
 https://hgdownload.soe.ucsc.edu/gbdb/mm39/vistaEnhancers/vistaEnhancers.bb