Since you were able to find another instance of invalid html links, I applied some regular expressions to locate others.... documenting here so I will fix them.
./A_thaliana_Jun_2009/LFYAtTile1R/HEADER.md:10:href="http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE28063">GSE28063</a>.
./A_thaliana_Jun_2009/LFYAtTile1R/HEADER.md:31:href="http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GPL10977">GPL10977</a>)
./A_thaliana_Jun_2009/cold_stress/HEADER.md:26:href="http://www.lorainelab.org">Loraine Lab</a> at <a
./A_thaliana_Jun_2009/cold_stress/HEADER.md:27:href="http://www.uncc.edu">UNC-Charlotte</a> in which we investigated
./D_discoideum_Ax4_May_2009/HEADER.md:11:href="http://www.transvar.org">Loraine Lab</a>) created all the files
./D_discoideum_Ax4_May_2009/HEADER.md:13:href="http://www.dictybase.org/Downloads/"> dictyBase file Download
./P_trichocarpa_Aug_2012/HEADER.md:21:href="http://samtools.sourceforge.net">samtools.sourceforge.net</a>
./D_melanogaster_Jul_2014/HEADER.md:11:href="ftp://ftp.flybase.net/genomes/Drosophila_melanogaster/dmel_r6.03_FB2014_06/gtf">ftp://ftp.flybase.net/genomes/Drosophila_melanogaster/dmel_r6.03_FB2014_06
./S_lycopersicum_May_2012/HEADER.md:12:href="http://samtools.sourceforge.net">samtools.sourceforge.net</a>
./P_patens_Jan_2008/HEADER.md:11:href="https://www.cosmoss.org/physcome_project/wiki/Downloads">Cossmoss.org
./P_patens_Jan_2008/HEADER.md:17:href="http://www.cosmoss.org">CossMoss</a>.
./T_parvula_May_2012/HEADER.md:7:href="http://www.bioviz.org/igb">BioViz.org</a>.
./T_parvula_May_2012/HEADER.md:30:href="http://samtools.sourceforge.net">samtools.sourceforge.net</a>
There are two instances of the "a href=" problem on this page: http://igbquickload.org/D_discoideum_Ax4_May_2009/