The issue here is that your Xara site, presumably developed for display on a desktop/laptop and how it displays on a mobile phone. Okay let's assume you've created your Xara site at 960 px wide. When viewed on a 21" PC monitor at 96ppi resolution on 1024 pix wide display (or greater) your site will look great.

Now you try to view it on a mobile. All you see is the top left hand corner of your site, about 25% of the whole home page. It's readable but you have to scroll your finger all over the place to read it. Is it any wonder? Average mobiles have a resolution of 360 x 480 px on a 4 to 5 inch screen, therefore your Xara created pixel perfect (960 px wide) site is going to do exactly as stated, show the top left hand corner.

Now it could be that you have an iphone5 with 326ppi display or a Samsung Galaxy S4 with 441ppi display and that will show all of your Xara designed home page on a 5inch screen, and as you state unreadable and therefore useless, but most mobile user don't have these hi-resolution phones so it's the Make & Model of the phone that determines how a Xara created site will display, not Xara software.

You would be better off offering your clients a far better service by creating a mobile friendly site, something that is difficult using a pixel dependant software but not impossible.

It's a case of one size doesn't fit all I'm afraid.