\\ is a comment in php, so using it in your links would screw things up. If you want to show an actual backslash in your text, use the html code \ wherever you want the backslash.
Like this,
<a href="https://www.ads-software.com/">WordPress \\ The Best CMS</a>
Shows,
WordPress \\ The Best CMS
See https://matrixmagic.com/tools/symbols.html for more about html codes.