why can't i override the font-size of the header

[Grace Yip]

why can't i override the font-size of the header

in my css file i have:

.ui-title{
font-size:14px;
}

when i run the app, there is no change ....

[Kateryna Grynko]

Here is the correct style:
code
.ui-header .ui-title {
font-size:14px;
}/code