iphone apps font change doesn't look like it should

Question

I've read here how to code the font exchange, I have two following questions,

1)why the actual font looks different from what it should look like

2)do i have to first install the fonts on my machine?

Answer 1

If you are using system fonts then its ok.

But to use custom fonts which are not provided by xcode then refer this

How to include and use new fonts in iPhone SDK?

EDIT:

To check fonts are added properly or not call this function and check names of fonts properly

-(void)checkFontList
{
    NSArray *familyNames = [[NSArray alloc] initWithArray:[UIFont familyNames]];
    NSArray *fontNames;
    NSInteger family, font;
    for (family=0; family<[familyNames count]; ++family)
    {
        NSLog(@"Family name: %@", [familyNames objectAtIndex:family]);
        fontNames = [[NSArray alloc] initWithArray:[UIFont fontNamesForFamilyName:[familyNames objectAtIndex:family]]];

        for (font=0; font<[fontNames count]; ++font)
        {
            NSLog(@" Font name: %@", [fontNames objectAtIndex:font]);
        }
        [fontNames release];
    }
    [familyNames release];
}