Submit button changes shape when hover

When I hover on the submit button on a form it changes in size.
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i know it's something in the template CSS, but i don't know what
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here's a link to the form: http://kvikpoulsen.dk/index.php/kontakt

Hi andyidel.
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"This site is down for maintenance. Please check back again soon."
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You can check the CSS using your browser web developer tools.
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Bob

sorry, the site is open now, i've checked the CSS, but i can't figure out what's wrong

Hi andyidel,
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It is the padding setting near the end of this CSS around line 994 of your template.css file

.art-button.active, .art-button.active:hover
{
  background: #A1ADBA;
  background: linear-gradient(top, #D3D9DE 0, #B3BDC7 50%, #8494A4 50%, #A4B0BC 100%) no-repeat;
  background: -webkit-linear-gradient(top, #D3D9DE 0, #B3BDC7 50%, #8494A4 50%, #A4B0BC 100%) no-repeat;
  background: -moz-linear-gradient(top, #D3D9DE 0, #B3BDC7 50%, #8494A4 50%, #A4B0BC 100%) no-repeat;
  background: -o-linear-gradient(top, #D3D9DE 0, #B3BDC7 50%, #8494A4 50%, #A4B0BC 100%) no-repeat;
  background: -ms-linear-gradient(top, #D3D9DE 0, #B3BDC7 50%, #8494A4 50%, #A4B0BC 100%) no-repeat;
  background: linear-gradient(top, #D3D9DE 0, #B3BDC7 50%, #8494A4 50%, #A4B0BC 100%) no-repeat;
  -svg-background: linear-gradient(top, #D3D9DE 0, #B3BDC7 50%, #8494A4 50%, #A4B0BC 100%) no-repeat;
  -webkit-border-radius: 3px;
  -moz-border-radius: 3px;
  border-radius: 3px;
  -webkit-box-shadow: 1px 1px 2px 1px rgba(0, 0, 0, 0.25);
  -moz-box-shadow: 1px 1px 2px 1px rgba(0, 0, 0, 0.25);
  box-shadow: 1px 1px 2px 1px rgba(0, 0, 0, 0.25);
  border: 1px solid #8A99A8;
  padding: 0 20px;
  margin: 0 auto;
}

Bob