Width and background problem

Hello.
The problem is not with background.
You was set the option “Unavailable days from today:” as 31 at the General Booking Settings page, so thats why the days in the August is not available and you are see the black background. Please send this option to 0, so then you will be able to select the dates during August 2013.

Also you are still have some CSS conflicts with the
http://hotel-challans.fr/wp-content/themes/simplekey/css/general.css
This CSS file is override some CSS attributes. For example the previous/next month links is not showing correctly, because of that.

1) For fixing of that issue, please open this file:
http://hotel-challans.fr/wp-content/plugins/booking/css/skins/standard.css

Find this code at line 162:

.calendar-links {
  float: left;
  height: 15px;
  margin-bottom: -35px;
  padding: 5px 0;
  position: relative;
  z-index: 0;
}

and replace it to this code:

.calendar-links {
  float: left;
  height: 15px;
  margin-bottom: -35px;
  padding: 5px 0;
  position: relative;
  width: 100%;
  z-index: 0;
}

2) Then open this file: http://hotel-challans.fr/wp-content/plugins/booking/css/client.css

at line: 207

find this code:

.datepick-inline {
  margin-bottom: 10px;
}

and replace it to this code:

.datepick-inline {
  margin-bottom: 10px;
  width: 285px !important;
}