function setFontSize(fsMod) {
	// fsMod muss entweder 0 sein (fuer standard) oder modifikator -x bis +y entspr. Arrays unten! (hier: -3,-2,-1,0,+1,+2,+3,+4,+5)
	
	if (!document.getElementsByTagName) return null;
	
	var baseObj = document.getElementsByTagName("body")[0].style;
	
	var fs_stdVal = "1em";
	var fs_stepsUp = new Array ("1.1em", "1.2em", "1.3em", "1.4em", "1.5em");
	var fs_stepsDw = new Array (".7em", ".8em", ".9em");
	
	var fSizes = fs_stepsDw.concat(fs_stdVal,fs_stepsUp);
	
	if (fsMod == 0) {
		baseObj.fontSize = fs_stdVal;
		newFontSize = 0;
	}
	else {
		var newFontSize = Math.round(fs) + Math.round(fsMod);
		if (newFontSize < 0) if (newFontSize < -(fs_stepsDw.length)) newFontSize = -(fs_stepsDw.length);
		if (newFontSize > 0) if (newFontSize > fs_stepsUp.length) newFontSize = fs_stepsUp.length;
		fId = newFontSize + fs_stepsDw.length;
		baseObj.fontSize = fSizes[fId];
	}
	fs = newFontSize;
}