how to increase size of text in web view

i have a web view and i want t开发者_如何学JAVAo increase size of text in it when i press button ...

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Try this:

[webView stringByEvaluatingJavaScriptFromString:@"document.body.style.zoom = '1.5';"]

This will zoom in all contents of the UIWebView by a factor 1.5.