function fontNav(tp){
		var tags = document.getElementsByTagName("td")
		var tam = 0
		for(var x in tags){
			if(document.getElementById(x)){
				if(document.getElementById(x).getAttribute("tp") == "conteudo"){
					if(document.getElementById(x).style.fontSize==""){
						document.getElementById(x).style.fontSize = 12	
					}
					tam = parseInt(document.getElementById(x).style.fontSize.toString().replace("px",""))
					switch(tp){
						case '+':
						if(tam+3!=21){
							document.getElementById(x).style.fontSize = tam + 3
						}
						break;
						case '-':
						if(tam-3!=9){
							document.getElementById(x).style.fontSize = tam - 3
						}
						break;
					}	
				}
			}
		}
	}