function checkForm(f) {
    
    var kw = f.keywords.value;
    kw = kw.replace(/</g, '').replace(/>/g, '').replace(/\./g, '').replace(/,/g, '').replace(/\'/g, '').replace(/\*/g, '').replace(/`/g, '').replace(/\$/g, '').replace(/\^/g, '').replace(/&/g, '').replace(/%/g, '');
    
    while(kw.charAt(0) == ' ') {
        kw = kw.substring(1, kw.length);
    }
    
    while(kw.charAt(kw.length - 1) == ' ') {
        kw = kw.substring(0, kw.length - 1);
    }
    
    if (kw.length < 4) {
        alert("To search for products please type in the keyword(s) into the text field.\nSingle keyword should be at least four characters long.\nThank you.");
        f.keywords.select();
        return false;
    }
    
    f.searchType.value = 0;
    
    if (kw.indexOf('+') > -1) {
        f.searchType.value = 1;
        kw = kw.replace(/(\s)*\+(\s)*/g, ' ');
    }
    
    kw = kw.replace(/(\s){2,}/g, ' ');
    f.keywords.value = kw;
    
    if (kw == 'Búsqueda') return false;
    return true;
}