It has been another busy week for many of Australia's top brokers. This has led to the release of a number of broker notes.

Three broker buy ratings that you might want to know more about are summarised below. Here's why brokers think these ASX shares are in the buy zone right now:

CSL Ltd (ASX: CSL)

According to a note out of Morgans, its analysts have retained their buy rating and on this biotechnology giant's shares with a trimmed price target of $303.70. The broker believes that CSL's shares are materially undervalued at current levels. It highlights that on an EV/EBIT multiple of 18.2x, it is more than 25% below its 10-year average of 24.7x. Furthermore, based on a conservative sum of the parts valuation, it estimates that fair value is $196 billion, implying around 35% upside from current trading levels. Morgans also points out that the market appears to be valuing CSL on less than a single division. Its calculations imply a ~10% discount to the core Behring business alone, while effectively attributing zero or negative value to the CSL Seqirus and CSL Vifor businesses. The CSL share price is trading at $240.73 on Friday.

South32 Ltd (ASX: S32)

A note out of Macquarie reveals that its analysts have retained their outperform rating and $3.60 price target on this mining giant's shares. The broker has been looking at the big miners ahead of their quarterly updates this month. Macquarie is expecting a bit of a mixed bag from South32. Copper production is expected to miss consensus estimates but alumina is expected to beat and aluminium and manganese are forecast to be in line. Outside this, the broker continues to see long term value in South32 shares at current levels and is recommending them to clients. The South32 share price is fetching $3.13 at the time of writing.

Web Travel Group Ltd (ASX: WEB)

Another note out of Macquarie reveals that its analysts have held firm with their outperform rating and $6.19 price target on this travel technology company's shares. Macquarie has been pleased with recent travel industry data, highlighting that US travel volumes are better than feared. In addition, the broker was pleased to see that hotel demand in Europe has been solid despite the conflict in the Middle East. Overall, Macquarie is feeling upbeat about the travel sector and particularly on Web Travel, which is believes has more resilient earnings than peers. The Web Travel share price is trading at $4.76 this afternoon.