var spEmStepWidth = 0.125; // increase/decrease font every step by spEmStepWidth
var spEmBasis = 1.25; // font size of spArticleBody at startup
//var spEmBasis = 1; // font size of spArticleBody at startup
var spEmStep = -1; // counter for current step (leave as 0)
var spEmMaxSteps = 2; // maximum steps alowed
/**
* spFontSizer increase/decrease font size inside "spEmStep"
*
* use: spFontSizer(1, false), spFontSizer(-1, false) or spFontSizer(0, true)
* @param spInc set to 1 or -1
* @param spReset set to true to get initial font size
*/
function spFontSizer(spInc, spReset) 
 {
  // reset font size
  if (spReset)
   {
	spEmStep = -1;
   }
  
  // inside allowed steps?
  if (Math.abs(spEmStep + spInc) <= spEmMaxSteps) 
   {
    // increase/decrease spEmStep
    spEmStep += spInc;
    // set new font size for every tag inside "spEmStep"
    spEmFontSize = spEmStep * spEmStepWidth + spEmBasis;
    //get spArticleBody
    spEmBody = document.getElementById('content_left');
    // spEmBody = document.getElementsByTagName('body')[0];
    // set new fot size
    spEmBody.style.fontSize = spEmFontSize + "em";
   }
   
 if (spEmStep == -spEmMaxSteps) 
  {
   document.getElementById("spFontsizeMinus").src = "img/FontsizeMinus_lo.jpg";
  }
 else if (spEmStep == spEmMaxSteps) 
  {
   document.getElementById("spFontsizePlus").src = "img/FontsizePlus_lo.jpg";
  }
 else 
  {
   document.getElementById("spFontsizePlus").src = "img/FontsizePlus.jpg";
   document.getElementById("spFontsizeMinus").src = "img/FontsizeMinus.jpg";
 }
}