fixed overflow on slide rendered images

public/scripts/functions.js

@@ -146,9 +146,10 @@ function slideBack(){
 	var actualId = actual.id.split("_")[1];
 	if(actualId > 0){
 		actualId--;
+		actual.className = "renderedCanvas";
+		document.getElementById("rendered_"+actualId).className += " visible";
 	}
-	actual.className = "renderedCanvas";
-	document.getElementById("rendered_"+actualId).className += " visible";
+	
 }
 
 function slideForward(){
@@ -156,9 +157,9 @@ function slideForward(){
 	var actualId = actual.id.split("_")[1];
 	if(actualId < document.getElementsByClassName("renderedCanvas").length){
 		actualId++;
+		actual.className = "renderedCanvas";
+		document.getElementById("rendered_"+actualId).className += " visible";
 	}
-	actual.className = "renderedCanvas";
-	document.getElementById("rendered_"+actualId).className += " visible";
 }
 
 function hasClass(el, cls) {